What kind of laptop should I buy?

I’m going to be entering college, fall 2009, and I’m an art major. I really don’t know what kind of laptop I should get. It seems that every art school uses Macs, but I’ve never used one before.

For preference, I want something that has high quality graphics (again, art major) and can run Photoshop and Illustrator well, has a lot of memory, and is relatively light.