This is not a complete list of what's available; think of it as more of a guide to start you off. First, some basic information. I've spent countless hours of research, design, editing, and coding to be sure that the Japanese dictionary set-up I've built this system around really is the best system around. The dictionaries described on this page are other people's work, not my own, so I can't make any promises about them. However, I use some of these myself and have had good reports about others, and the ability to add specialized vocabularies and databases--and other entire languages--to the Axim is one of the things that makes it so much more powerful than a mere electronic dictionary. One hint, though: installers for most dictionaries and dictionary programs will try to install to the main memory, which is a limited resource. However,dictionaries will run just as well from the larger Built-In storage or a memory card, so I recommend clicking "No" when an installer asks you if you want to install to the default directory (it'll then ask where you want to install the program/dictionary). In the new (from March `08 on) English system, it's a bit easier--the Axim itself will ask you if you want to install any program to the device itself (main memor) or a memory card--choose one of the cards.
One note on fonts: The Japanese version of the JLT system comes with the standard Japanese font--it includes characters for Japanese, English, and some European languages, but lacks some characters from other languages, including Chinese hanzi that aren't also Japanese kanji. The new English system uses a much larger font with all Chinese hanzi and most European languages (you can also enable a font with Korean and Korean and Chinese input systems as well as the Japanese). If you're interested in using the device for Chinese or Korean, you should go with the English system. If you're interested in using it with other languages, please let me know on the inquiry form at the bottom of the order page so I can check on the compatibility--when I reply, I'll ask you to send me a sample document in the language and a link to a website in the language so I can see if they display properly. Quick note: it seems the iPAQs I'm using for the Japanese version now include more languages in the font set than the Axims I used to use--so for a given langage, I might recommend the English or Japanese system or say that either should be OK.
My system uses the EBPocket program and dictionaries in the EPWING format. There are quite a few other EPWING dictionaries you can install and run with EBPocket, if you like. Many of those are free. You can spend a lot of time looking for free dictionaries online; I've found that Maximilk's site is a good place to start. Some of the most useful free offerings I've found are below. If you buy a JLT Complete System, all the free dictionaries immediately below will be included on the backup DVD--simply copy one to the memory card, put the card back in the PDA, and use Edit Group in EB Pocket to install it. Don't install dictionaries you don't really need just for the heck of it, though, as having many dictionaries activated will slow EB Pocket down.
I'll gladly install any of these free EPWING dictionaries free with your purchase of a complete system or memory card. There's a decent Japanese-Spanish EPWING dictionary that's not free but is nearly so--I can install that for just 1500 yen to cover the license fee.
There are also numerous commercial dictionaries available in EPWING format (I also include Logovista format here because it's very close to EPWING and can be transformed to EPWING easily). The main ways to get these are to buy EPWING or Logovista versions on CD-ROM or downloading from Logovista's site (if you've got a need for anything Logovista offers, you probably already read Japanese well enough to navigate their site). I think the most useful commercial dictionary is Daijirin, a well-respected authoritative Japanese dictionary. The alternative to Daijirin is Koujien, the Japanese-Japanese dictionary regarded as the most authoritative--but it reflects classical and historic usage more than contemporary usage, so most foreign language students find Daijirin more useful. Most standard electronic dictionaries used to include Koujien, but many of the higher-end units are switching over to Daijirin. Kenkyusha Intermediate is a Japanese-English dictionary that some people like because it's the dictionary installed in many standard electronic dictionaries, but to be frank I don't think it adds anything worthwhile if you've already got Eijiro; Kenkyusa Daijiten is much larger and more useful, but so much more expensive that I don't think it's worth it for most people if they already have Eijiro. Some advice for finding and installing EPWING dictionaries yourself is on my tech details page. I'll gladly buy and install Daijirin, Koujien or Kenkyusha for you for the prices listed on the order form, and any other commercial dictionary for 1500 yen (with complete system purchase) or 2200 yen (with card purchase) more than the complete purchase cost (including tax and shipping) of the dictionary.
Like EBPocket, the free Pocketdict is strictly a dictionary reader program--it doesn't include dictionaries, but there are a huge variety of free dictionaries available for it. (Full disclosure: I tried and rejected PocketDict when trying to find the best set-up for the Japanese system--it wasn't up to dealing with the huge Eijiro dictionary, and it didn't work as well as EBPocket. However, all the available dictionaries for Pocketdict are much smaller than Eijiro and should be OK.) Simply Google "pocketdict" and your language of choice and you'll likely find several options (often smaller older versions and larger newer versions of the same dictionary are available, so look around for the newest one).
Another free dictionary program with many free dictionaries available. Also not as good as EBPocket (lacks the powerful search features that help EBPocket tame the massive Eijiro so elegantly and a few other features necessary to the main JLT dictionaries), but there are many, many free dictionaries available for it. It has one great feature Eijiro lacks--it lets you highlight a word in any other application (browser, email, word document, even EBPocket) and instantly pop up it's definition in a small window--used with Edict (MDict version called JMDict) it's great for looking up Japanese words. If you use the excellent rikaichan add-on for Firefox, this function will be familiar to you--but it works in everything you do on the Axim, not just browsing the web. Also, if you have 2.7 GB of free memory card space, you can install the entire text of the English version Wikipedia to access through MDict--you can use Wikipedia any time, anywhere, without having to go online. JLT systems all come with MDict and its version of Edict installed; X51V systems also include the MDict Wikipedia. See here for more details.
Many companies make dictionaries for the Pocket PC. Just be sure the program you want is compatible with Windows Mobile. Several of my customers have installed and recommended Mobisystems and Lingvosoft dictionary programs; these companies offer a wide variety of languages in what seem to be well-designed, comprehensive dictionaries. Oxford also makes some good, reasonable priced dictionaries for Windows Mobile. There are thousands, perhaps tens of thousands, of dictionaries and dictionary programs for Windows Mobile--use any search engine to find them on the internet.