I've recently got back into chess in a big way but last night took a hammering from my friends (despite the fact I'd subsituted one of my rooks for a Dalek from Doctor Who). This prompted me to get some much-needed practice in, so I installed the bizarrely-named TeKnowMagic Chess on my Pocket PC.
The graphics aren't very good but the game itself includes three levels of difficulty and one or two player modes. In addition, it includes options to customise the game board, changing colors environment, activating/deactivating the sound, among other possibilities.
If you're a beginner then don't expect much help from this game, but if you're looking to hone your chess skills and progress in difficulty TeKnowMagic Chess represents a nice way to do so on the bus.