Here are a few sites I like:
Trendistic – Twitter tool that allows you to search and track specific keywords, and see trends for them
Tweetbeeps – Keep track of conversations that mention your company, brand, topic.
Bit.ly – You can track who has opened your shortened link versus total clicks for all bit.ly links pointing to the original long URL
KnowEm.com alerts – Weekly e-report of where your user name appears across more than 200 social media sites. This comes with their service to create profiles on SM sites.