I usually recommend a Mac mini, which is what I used, until the new 13" Macbook Pro came out, to create my app. The mini is also hooked up to my 42" flat screen, so it serves a dual role as a media center in addition to app development.
However, given the price of the non-Pro Macbook 13", and an Education discount ($100 off), and free iPod touch for college students/faculty. Assuming you qualify, that might be a good combination. About $950 and you get a $200 iPod touch which would be helpful for development, plus it's portable and no need to add a monitor, etc. Look into it. If you go to store.apple.com, and click on Education, they don't seem to be as strict as if you go to the store, which I did. I had to login to my wife's (college professor) email account as proof.