A lot of stuff has been coming up about Social Media and Buzz Monitoring (which is current and pro-active) while Web Analytics and Audience Data is reactive and backward looking - but figuring out what package is best (if any) usually takes working with the software and seeing if it's useful for what you need.

Monitoring Social Media Before You Have a Budget by Nathan Gilliatt gives a list of those which are free or that you can try out before you have to pay anything.

Interestingly, someone from one of those platforms on the list, Radian6, will be attending the Social Media Roundtable in Toronto next week, and I'll be there.

Another interesting development which I just heard about is Measurementcamp - a group meeting in regularly in London to create a set of open source resources which allow interested parties to measure their social media communications online and offline.

I don't know much or anything about Measurementcamp but know a few people  living nearby and one of them, hopefully, will attend a future meeting of  the  Measurementcamp.