I spend a lot of time on the bus and have been enjoying two apps I found, one which quizzes you on countries of the world
and one which quizzes you on human anatomy
. Both are really fun, and now I know the locations of both Lesotho and my capitulum! (They are not in the same place.)
I've got a Droid, but feel free to recommend apps for other types of phones. Please recommend anything that *you* find neat, but if you wants topics of interest, mine include: anything to do with science or history especially, anything to do with statistics, math, engineering, computer science, language learning.
I know that I like the quiz based apps that just help you memorize a lot of useful information, but if you have a different type of app to recommend, feel free! There's a lot of stuff to know that can't be easily formulated as a quiz game.