Been a while since you looked at your privacy settings? AdjustYourPrivacy.com collects all the most important privacy settings for multiple services so you can opt out from everything you don't want from a single location.
This isn't the first site of its type, but AdjustYourPrivacy is one of the most complete collections of privacy settings we've seen yet. It isn't so much a service as a collection of links to useful places. You can adjust your settings for services including Facebook, Twitter, YouTube and Google+, as well as opt out of people-finding sites.
It also has links to useful services such as previously mentioned AccountKiller and HTTPS Everywhere, so you can really sort out your privacy. Whether you're looking to clean up a few things here and there or disappear from the internet completely, it's a useful place to start.