(if you've already got your PDA, skip to the next section)
First of all, the basic equipment. Which PDA to get? The short answer is, if you don't already have a Palm OS PDA, don't buy one. Japanese input options on the Windows Mobile PDAs are vastly superior to those on a Palm, even if you can find a native Japanese Palm like a Japanese version of one of the old Sony Clies. The dictionary software available for Windows Mobile is also much better. If you want to use a PDA for Japanese and for dictionaries, you really should get a WM system instead of a Palm. I actually like a lot about the Palm OS--it's just that it doesn't accommodate Japanese very well.
However, if you already have a Palm and don't want to spend money buying something else, you can build a usable system that gives you access to some fantastic dictionaries, and still offers the key advantage of being able to look words up by either kana or kanji--even on the cheapest old Palm you can find, a Super Dictionary system will be easier to use and more powerful for non-Japanese than any ready-made denshi jisho (Canon Wordtank, etc.).
Pre-step. If your PDA isn't already capable of handling Japanese, the programs in Step (2) and most other programs for Japanese require that you first install a Japanese language environment, which will allow you to enter and display Japanese characters. PAdict doesn't require this and it's quite likely that beginning students will be more than satisfied with PAdict alone; I don't think KingKanji requires a Japanese environment but I'm not sure.1. Download and install PAdict, including the optional Big Dictionary. Instructions on the PAdict site. Cost: Free.
2. Two options:
3. (Optional) Download and install KingKanji ($25), or any other flashcard program you like (free ~ $???).
4. Add whatever other software, linguistic or otherwise, that you like.
PAdict is the best Japanese language tool I've seen, and it's a free, open source project that is continually being improved. Suffice it to say that almost everyone who's played with mine ended up buying a PDA, downloading PAdict, and using it as their main electronic dictionary, even people who already had big expensive Wordtanks. Once you try it out for yourself, you'll want it--ESPECIALLY if you've been using a denshi jisho for a while. Main advantage: it's made for English speakers learning and using Japanese, not the other way around. Coolest features: can enter kanji by writing it with the stylus; animated stroke order diagrams; save words to a hotlist for later study and review. Most useful feature: when you look up a word, you immediately have all the information right in front of you on one screen: kanji, hiragana pronunciation, English definition. Weaknesses: only one dictionary, Edict; English search function in Edict is sometimes less than ideal. However, beginning students may find that it offers everything they need for some time.
WDIC is a great dictionary program: it handles multiple dictionaries smoothly, even huge ones, has fantastic superjump and history features just like the best denshi jisho, and, best of all, it runs Eijiro and the complete Edict beautifully. (Just like iTunes is a program that plays song files, WDIC is a program that plays dictionary files; WDIC without any dictionaries is as useless as a music player without any music, and a dictionary without a program like WDIC is just a file that you can't open and use.) Eijiro is the most complete dictionary resource available in electronic form (note that my improved version of Eijiro, with yomigana, is NOT available for WDIC). Also add my versions of the complete Edict dictionary (reworked to give better English search results than the version in PAdict), the complete Enamdict dictionary of proper names, and the Kanjidic dictionary (rather obvious), all from the Edict project, along with my supplemental custom dictionaries, which greatly increase the usability of Eijiro, Edict, and WDIC for us non-Japanese, and you've got the best dictionary package available for ANY platform, including the great big one sitting on your desk (the Readings Dictionary gives you the ability to look words up by reading and to find out how words in Eijiro are pronounced, something you can't do in Eijiro as you get it from the maker; Conjugations shows you how to conjugate any verb you look up in the Edict dictionary). Even if you don't want to spend the money or use the memory card space for Eijiro, you'll do very well with the Edict Project files (even if one has PAdict, which uses the same base Edict database, the improved lookup of English words and the Enamdict proper name dictionary might make it worthwhile to install WDIC and my dictionaries, especially if one lives in Japan; if one spends much time talking to real Japanese or any time trying to read it, then WDIC and Eijiro are necessities). You can also use WDIC to look up a word in any other application, including PAdict, so you can use the amazing kanji look-up features of PAdict to enter one or more kanji from the word you want to look up, then instantly look the word up in WDIC. You get the best parts of each program, working together seamlessly. Go to my WDIC page to download WDIC free from the maker and all the dictionaries except Eijiro (which you'll have to buy from the maker, but at only 1980 yen it's a tremendous bargain)--these same files will also run on PDIC on your desktop.
KingKanji ($24.95) is a fantastic way to learn and study not only individual kanji but also words. And it's much more than just a flashcard system, making it fun to use, so much so that I actually find myself running through card sets instead of playing games when I've got time to kill. It beats the heck out of some fancy system that I won't actually use enough to benefit from. Best of all, there are many ready-made study sets for all sorts of specialized needs, as well as general study, use with specific textbooks, and for specific tests (I'm going to tackle the nikyuu set when I'm ready). The handwriting recognition is great--I find I remember things faster by writing them than just by passively looking at them. KingKanji is also available for Pocket PC.
KDIC is a great dictionary program--I was thrilled to find it, used it for a long time, and I still love it--but WDIC has turned out to be much better. KDIC doesn't handle multiple files and huge dictionaries as well as WDIC, and it lacks the history and superjump functions of WDIC. It won't run files as large as those in Eijiro. But for anyone who won't abandon KDIC, here are links to the full Edict dictionaries I made for KDIC and some how-tos. I won't be updating the KDIC files; for more up-to-date versions, you'll have to make your own (you can start with the text versions of my files) or turn to WDIC. There are a lot of great custom dictionaries available for KDIC, but it's usually pretty easy to adapt these for WDIC or to find .dic versions.
Palmdict is a promising program but it's got too many problems to be usable right now. The worst is that it crashes my Clie every time I try to quit; other users have reported the same problem with other Sony Clies and the PalmOne Tungstens. The other major problem is that it doesn't put the most likely results at the top of the search results window. I looked up "horse" and got 20 or 30 screens full of results; after scrolling through 10 screens of things like "dark horse," "horse of a different color," and "horse around," I still hadn't found the Japanese word for "horse." It shouldn't take 15 minutes to find the word for "horse." WDIC would put plain and simple "horse" at the top of the list. This flaw would be a serious pain in the neck, even if they fix the crashing thing.
Dokusha is widely touted on the web, but the dictionaries for it are based on an old and much smaller version (20,000 entries) of Edict, and the program for converting one's own files to Dokusha-readable databases is no longer available. With such tiny dictionaries, it's not very useful. It looks like the Dokusha project was abandoned several years ago.
英辞郎間引きツール (Eijiro Thinning Out Tool) is referred to in several places online, and I finally figured what it does (I think): it cuts out most of the Eijiro entries, leaving only about 200,000, and does some basic formatting to turn what's left into a KDIC file. It looks like it's pretty crude, choosing which entries to cut and which to keep on the basis of length. There are a bunch of "thinning" programs out there. They seem to be older, and they seem to have been put together on the premise that KDIC and other programs can't handle millions of entries. I don't see any need for a program like this when you can easily put the entire Eijiro on WDIC.
The standard commercial dictionaries: Kenkyusha, Readers, Genius, Koujien, Daijirin, etc.--these are exactly the same dictionaries that are built into all the leading denshi jisho, now available on CD and by download at Logovista, among other places, but they are much more expensive than the other resources I've mentioned (and much smaller than Eijiro). You might get a good deal on a used CD through amazon.co.jp. If you don't mind dropping a few extra dollars to make your PDA exactly like your Canon Wordtank, it might be great to have these along, though to me they don't seem necessary. The software versions, if converted to work with PDA software and run concurrently with my Readings dictionary, would work much better, even on the PDA, than they do in denshi jisho, where the ability to look up Japanese words by how they're written is highly restricted by the software. If you're having a hard time adapting one of these to run on your Palm or PocketPC, I'm always looking for an interesting project, so drop me a line. I've already got it figured out for Epwing and Logovista format dictionaries, and others shouldn't be too hard.