I got on a fix today about ads on websites, I already use Adblock Plus as well as the Adblock Filterset.G Updater in Firefox.  But I wanted to take it a step further.  I adid so with the following steps.

Opened up terminal and added the following list to my /etc/hosts file.
http://www.mvps.org/winhelp2002/hosts.txt

After this you need to flush the DNS cache

sudo dscacheutil -flushcache

All set.  You can of course use this on Windows/Linux and other versions of OS X.  For older versions of OS X the dscacheutil command is not the same.