Web 2.0 for scholars

Recently, I was reading the May 2009 edition of Educational Researcher and I came across a mention of citeulike. This is an online community where researchers can post article references that they like, rank them, and tag them, so that others can search by tag and rating and find some good articles. It's not too populated at the moment, or at least as populated as I thought it would be, but I like the idea. Especially since I'm pretty new at this and I like to know that an article is valued by the community before I spend a lot of time trying to understand and incorporate it into my work.