SuperMemo
http://www.super-memo.com
SuperMemo will help you forget about forgetting. This is the world's best speed-learning software.
Recommend:
SuperMemo2006 for PC
SuperMemo4.2 for PPC

MDict
http://www.octopus-studio.com/index.en.htm
MDict is a multi-language dictionary under WinCE for PDAs, 2008-5-7 MDict 2.5 Released!

Dictionary data resources:
http://down.maxpda.com/download/mdict/
http://bbs.pdafans.com/viewthread.ph...ct%B4%CA%BF%E2
http://bbs.pdafans.com/thread-362590-1-1.html