u can use opendns...i use it to filter sites at my work place, blocking out porn sites, videosharing sites, and others. all u do is create an account and wen u setting it up u select the categories of content that u want to block. once u do that u set ur machines to point to opendns server dns servers. in my case i only had to change one machine which is the linux box i have running as the gateway. i configure server 2003 which issues ip and dns resolution, to forward all out bout dns request to the gateway.
if u want to block a site that isnt under any category u can block it manually and also submit it to be blocked and add to a category. once enough ppl agree with u then it is added to a category
To find what you seek in the road of life, the best proverb of all is that which says: "Leave no stone unturned." Edward Bulwer Lytton