I am not sure if this is the solution you're seeking, but I might as well suggest it. Its really non-geeky though
Create an account at opendns.com
Follow the instructions on how to change your DNS-server settings locally.
At your opendns account you can set it to block certain sites. Perhaps you better start with checking that it actually has the specific blocking option you were wanting actually, so you don't do everything else in vain.
