People search engine Spock.com has opened up their beta to the public.
I previously described Spock as "ZoomInfo meets LinkedIn". At its most basic, Spock is a vertical search engine focused on people.
Spock leverages existing social networks to build its database. When you first register, it invites you to upload your address book from Plaxo, LinkedIn, Gmail, Yahoo or AOL. This helps them quickly develop a current database of people.
While social networks like LinkedIn and Facebook have garnered much of the recent attention, often you just need to find somebody - either by name, by company or job function. Vertical search engines like Spock and ZoomInfo are incredibly useful for this task. While you may not spend hours on Spock, adding apps and posting your favorites, it's likely you'll visit frequently when prospecting or recruiting.
Note: Spock.com apparently received more traffic than it expected today, on its first day of the open beta. So, if performance seems sluggish, give them a couple of days to get things worked out.