The 12" iBook is probably what you want.
If I were in your position, I would get a iBook with minimum 512MB of ram (if you buy from Crucial or another RAM supplyer it's a LOT cheaper. (
Here is the link for Crucial's iBook memory page....It's 63$ cheaper to buy a 512 upgrade from them).....Only do this if you are sure you know how to replace the RAM in your iBook (not a terribly difficult thing once you have the instructions, but none the less)
As for the hard drive size, that's up to you. If I was in your situation, I would upgrade to the 60GB hard drive since you may accumulate a lot of data in college. As I said though, this is your choice.
The reason I reccomend the iBook is because of its durability and overal functionality/portability. As a college student, you'll probably find that there are many cafes around campus with open WiFi networks, and your iBook would be ready to use those networks. You can take the iBook to class if you need to, and it will last longer than a powerbook (and be cheaper) due to its rugged form factor.
I hope this helped

Good luck with choosing a computer. I'm sure no matter what you get, it'll be right for you.
Oh yeah....If you're looking at the eMac as a possible solution, wait until January to make your choice. New eMacs are coming.