One of the easiest and cheapest ways to track mentions is to set up Google alerts. There are a variety of apps that monitor Twitter as well. Facebook is more difficult because most stuff on the network is still private.

If your willing to pay for a service their are countless maturing in the monitoring and engagement space.

http://www.radian6.com/ http://www.trendrr.com/ http://www.scoutlabs.com/ http://www.viralheat.com/

There are other I am sure I am missing, pry some good free ones out there too.