As in tools for using Twitter, not tools on Twitter (though there are plenty of those!). I may review a few this week. The first one’s easy, useful, and unlike some of the other ones, actually works.
The site is Backtweets. Search for a URL and Backtweets shows you who has linked to it on Twitter, including links that use URL shorterners. It’s a great tool for tracking commentary about your blog.
I’m currently testing out a few Twitter apps that are a lot more complicated and running into some problems. If I get them working I may post about them tomorrow.