Ubuntu is widely used for a variety of reasons. Mint is along the same lines. Both are easy enough to use.
If you really want an apple and are worried about price, I reccomend shopping Apple's refurb store and/or checking
http://dealmac.com/ under the "systems" section - they often have discounted mac laptops as low as 600-700, and also good deals on mac minis and iMac's. I personally bought my mac new, using a student discount, and sold the free iPod that came with it. There are a few ways to avoid paying full price on these
