i've seen a lot of people just use their ipods. if i had one, i'd use it. i have an olympus from costco. it's neat cuz you could download lectures onto your computer if you need more room. i think it only holds like 5 hrs or so. and it's worked out for friends cuz i've burned them CDs if they weren't able to catch everything in lecture.
also check out the livescribe, that one looks REALLY neat!
oh, and some people just use their laptops to record. its cheap.