In years past, I'd suppress my inner Mac booster and point out that you should weigh the school's operating system suggestions (which typically means Microsoft Windows) in your deliberations, and I'd note in fairness that a Windows laptop can be better suited for some people.
Boy, am I glad I don't have to do that anymore.
Get a MacBook.
As we've discussed in this column before, the Intel-based MacBook can run Windows, either directly using Apple's Boot Camp beta (which was recently updated to version 1.1 and will appear as a full-fledged feature in the upcoming Mac OS X 10.5 Leopard, www.apple.com/macosx/bootcamp/) or using virtualization software such as Parallels Desktop (http://www.parallels.com/).
If your school requires you to use some Windows-only software, you can simply launch Parallels and run Windows within a separate window in your Mac OS X environment, or restart the machine from Windows using Boot Camp.
The Seattle Times: Business & Technology: Best computer for school? MacBook