Really easy setup but by no means foolproof
I use OpenDNS at home, and it does seem to block a bunch of stuff, but it really can't block many things because of the way it works - as a DNS blocker. Either you block all of Youtube or you let all of it through. Google image search is handy so you let that through, yet it can also return many thumbnails you might rather block. My son also managed to find a number of websites that it should have been blocking completely but wasn't! Finally, it is pretty simple to circumvent if a user has access to change their DNS settings (which they may well have on a mobile device, etc.).
However, it is very simple to set up, and as I have DHCP on the router set to point clients to OpenDNS's DNS servers it covers all devices on the network (mobile phones, Sony PSPs, Wii, etc.) automatically, rather than just the main desktop that you've installed it on: the way some other filtering programs work.
