I am always on the lookout for the latest and greatest e-reader. When I found out about the latest Nook Wifi (cost US$149), I was very impressed by it. It is very similar to the Amazon Kindle Wifi (cost US$139) in terms of features and price.
Nook Wifi: http://www.barnesandnoble.com/nook/features/index.asp
Kindle Wifi: http://www.amazon.com/gp/help/customer/display.html/ref=hp_navbox_top_kindlelgi?nodeId=200503360
I can tell you all the pros and cons of each, but I'll list the most significant ones here. One deal clincher feature me is the fact that the Kindle allows you to rotate the screen in any four directions, while the Nook doesn't. This is extremely critical because when you are reading a pdf book, the landscape orientation makes the font larger and much more readable. You can find a lot of good free books in pdf, but not in other formats.
The Nook's greatest advantage over the Kindle, on the other hand, is the ability to read any epub book (with or without DRM - digital rights management). Kindle doesn't. This is not a problem for me because I can use Calibre (3rd party software) to do format conversion, but it may be a serious problem for non-techies. Epub is the predominant format among ebooks, hence opening up your choices if you are shopping for ebooks.