Well, Mac wise, go for a Powerbook G4. Should be an excellent system for any art/photography major. Out of the box, you get a great photo managment program. Beyond that, all the typical Adobe apps and such exist, and run fine.

Make sure you check your school for any student discount. Use this link to see your discount. Note the price on what system you want. Then use this link and add $100 to what you see as the price there. Basicially the second link is to the Apple Developer store, and as a student, you can register as a developer for $99, and use the discount once.

Powerbook wise, it's going to depend on portability vs screen size. The 17 inch should be fine on its own, but the others, you may want to grab an external monitor to work on things while in the dorm.

*edit* One reason I say go for a Powerbook over an iBook is the ability to hook up an external monitor and use it at a high resolution, something the iBooks can't do. While an iBook does feature an external monitor port, it forces you to use the resolution of the laptop on it, and the iBooks limit is 1024x768, probably not a good resolution for serious Photoshop work.