Hm. Well, it depends on how you want to take notes. If you want to type your notes, there might be some cheaper netbooks to look at. With Google docs, I find anything that can run a web browser will work, so there may be some inexpensive netbooks around. I believe you can import power-point documents as well. LibreOffice is also a nice alternative.
Another option would be a tablet. The only issue is that most tablets (good ones anyway) fall a bit out of your price range.
One thing that may/may not work are those digital pens- they record both the audio of your notes, as well as the physical notes themselves.