Ghostery is the best! I have it for both Safari and Firefox. It is just amazing to see how long the list of trackers can be.
I'll say. I've seen some websites that have over twenty activated.
Good thing about Ghostery is, once you've disabled a particular tracking program, it's disabled for any website that employs it.
I've disabled so many now, that it's rare for me to check a website and find one that I haven't already blocked. Great tool, and simple to use.