Web search has lots of power when it comes to Social Media monitoring, there are lots of free tools and search engines that can help you in that area. Combine the search results with rss feed, and you will get an easy way for tracking the social media. This can be very useful in watch-and-warning teams and security monitoring activities.
Monitor blogs, comments, news, tags, forums,...
Yacktrack (comments on defined URL)
Search for People:
Tattler, Open Source Topic Monitoring Tool
A comprehensive list is now available on http://wiki.kenburbary.com/social-meda-monitoring-wiki/