Consolidated Jewish Surname Index (CJSI) - several databases combined, 2,000,000+ entries.
Excellent databases, however most now require fees. Most useful to me:
The Social Security Death Index - Previously free database of the deceased, whose relatives applied for the death benefit from the Social Security Administration. Contains 71,265,046+ names.
Great, free resource for finding people's current ages and locations.
Gives exact birthdays and current zipcodes of registered voters/licensed drivers. Because of these parameters it does not contain as many individuals as US Search.
It is with sadness that I list a link to such a site; however, it has been a source of information.