Jim Stroud, the wonder behind The Recruiter's Lounge, has a short tutorial up on searching for candidates using Flickr. It's the first in a three part series.
Flickr is a photo sharing site, one of the two most popular, and the reasons for searching on it are 10 passive candidates, and 2) social media savvy passive candidates. The hit rate might be low on return, but that's true for anyone not on a job board.
One thing to add to Jim's searches, is to have your own Recruiting Flikr account, which pictures and text describing why a candidate would want to come work for you. While you're at it, duplicate your work on Photobucket and Snapfish.
It will increase your return on messaging, and also serve as a pull marketing component as images in Flickr show up in Yahho and Google related image searches.
