Given those parameters, I'd look at a refurbished MacBook. (Look on the lower-right part of Apple's online store--the refurbished section is a little hard to find.) Apple's refurbished gear is good as new, from my experiences; I've bought two items as such (one Mac mini, one 5G iPod), and you'd never know they weren't brand new once you hide the box.
There's a base-model
MacBook for $899. If you've got a little extra money to spend, I'd look at buying more RAM to upgrade with (you can do fine with 512, but getting at least a gig is nice).
Treat it right, and it'll certainly reach the five-year mark.