You might consider taking a look at the
Sony PRS-350, especially now while it's on sale for $129. I recently got one during the sale and absolutely love it. The small size lets me take it everywhere, the touch screen requires just a slight thumb movement to advance pages, handles epubs and pdfs well, e-ink screen, and probably one of the lightest readers on the market (if not the lightest).
If you don't require your reader to connect to a wi-fi and prefer (like many of us) to transfer your books from your PC to the reader, then it's definitely worth a look. There's plenty of posts around from users about theirs to check out more info about it.