One of the most frustrating things for me is learning similar-looking characters. Last year I grouped a bunch of similar-looking simplified characters together and incorporated them into a game for the iPod called Trevor's Chinese Memory Game.
http://itunes.apple.com/us/app/trevors- ... 19519?mt=8
Right now it's pretty simple (though it does include over 3000 characters) and I'm working on some new features to be released by the end of February.
In the mean time, I'd be interested in your feedback.