well, you ask what's it good for.
But I'm going to ask what's it not good for?
Seriously you can do almost anything with a computer right now.
I use it everyday for
talking to friends
watching movies/tv shows (don't even have a dvd player at home, no need since my monitor is bigger than my tv
listening to music
using forums like this one (great for learning stuff and helping people)
a computer can be used for so many things it's not even funny.