measuring social media effectiveness

We're looking again at this topic so wanted to post some links to other companies in this space:
http://www.mediamiser.com/
http://www.attentio.com/
http://www.marketsentinel.com/
http://www.nielsenbuzzmetrics.com/
http://www.biz360.com/
http://www.jdpower.com/
http://www.buzzlogic.com/
http://www.cymfony.com/
http://www.motivequest.com/
http://www.onalytica.com/
http://www.wavemetrix.com/
http://www.cicdata.com/
http://www.radian6.com/
http://www.relevantnoise.com/
http://www.unica.com/
http://www.millwardbrown.com/
http://www.lotame.com/
http://www.converseon.com/
http://www.visibletechnologies.com/
http://blog.collectiveintellect.com/
http://www.corextech.com/
http://www.blogscope.net/
http://www.sentimentmetrics.com/
http://www.socialtarget.com/
http://www.measuresofsuccess.com/
http://www.umbrialistens.com/
http://www.factiva.com/