A very useful and cool tool for on-the-go learners of Mandarin Chinese. Almost everyone these days has a cell phone and, with this application, learners can make good use of them for studying Mandarin Chinese when they get a spare moment or are in transit!
The basic principle is fairly simple - the program shows a word in one language (either English or Chinese), then displays the pinyin (Chinese pronunciation) of the word and finally gives the word in the other language. You can choose whether to go from English to Chinese or from Chinese to English, and also other options like whether to view words in order or in a random order, and whether or not to remove cards after a certain number of successful answers.
At the moment the program comes loaded with seven word lists at different levels, and you can also add your own lists in the CEDICT format (it's a little tricky to do this, but nothing too difficult).
To use the flashcards your phone needs to support Java (MIDP2 / CLCD 1.1), which should be no problem for most phones bought in the last couple of years, and to see the Chinese characters you need to have Chinese fonts installed as well.
I've changed the program's license from "no derivative works" to "share alike", meaning that you're free to add your own word lists and share the altered program with whoever you want, as long as you let other people do the same thing with the changes you make. I plan to eventually open-source the software, but I don't want to do so until version 3 of the GPL becomes available - the current version does nothing to stop anyone from applying DRM to GPL-licensed software, and DRM unfortunately all too common in the mobile industry.