Topsy: New-ish Twitter search engine that provides a ranking of your popular tweets, and attempts to navigate the network of links between your tweets, retweets and more. I think we'll see many more of these sorts of popularity tools for Twitter pop up over this year as the general public tries to make sense of it.

Compare My Docs: I can see the plagiarism checking benefits for this (by comparing source material to essays) in addition to the versioning comparison that the site is aiming at. Sure, Turnitin is more robust, but it's also a pay-to-play service.

WordPress Opens Up in an effort to improve their overall design and user experience. I never really found WP to be that bad, although at times I can see how user experience can be improved. A good idea to outsource this to the crowd, we'll see the results fairly soon I suspect.