Go to freeappalert.com every day and you'll soon be swimming in apps, and won't have spent a cent.
Games
Ragdoll blaster (and #2) - physics + humans + cannon + puzzles
Warpdefense - halfway decent tower defense. Perhaps too easy, but I got it for free, so meh.
Boxed In (and #2) - warehouse puzzle game - push the boxes to the right spots
Doodle guess/search/ships/etc - pretty decent two player games
Babylon Twins - fun sidescrolling puzzle game
Sudoku Guru - If you like sudoku, this is a pretty nice app for it.
Media
Pandora - Music! Free!
SpaceGeek - What's NASA up to lately? Live braodcasts - nice for lauches
NASA - NASA's app, sorted by missions. Some multimedia stuff.
NPR - Nice to be able to listen to Diane Rehm and other NPR programs on demand. Car talk and wait, wait, don't tell me are two funny shows you might get a kick out of.
Utilities
Packagetrackr - Track packages, ups, fedex, dhl, usps, etc
Air Mouse - control your computer from afar (great for watching hulu, etc)
Square - accept credit card payments for your garage sale, or whatever
EasyExit - if you drive a lot with kids, then being able to predict whether the next exit has food, gas, lodging, etc is very nice.
Facebook - if you don't know, then don't even start
iRelax - Get to sleep with a good selection of noises (I do Rain, Winds, and Thunder, sometimes with ocean...)
Quakes - see where recent earthquakes occurred
Skype - Phone home... (I guess you need a mic for this...? I don't know if the touch has a built in mic...)
Keep in mind that I'm a cheapskate, so the vast majority of stuff I have is either perpetually free, or was obtained from freeappalert.
I've also left out a lot of apps I use that make good use of the gps. While they would be usable on your ipod touch (depending on the availability of wifi stations nearby you) you probably would not get much use out of them.