San Francisco designer Gabe Ruane has launched the Identity Archives Project, a growing online database of logos submitted by their respective designers worldwide. Anyone can submit a logo, providing it "is/was a client approved design, and that it is/was in use publicly." With enough contributions, the site will function as a great resource for researchers and a pit-stop for designers wanting to avoid accidental logo look-alikes. So dig through your personal oeuvre and start uploading!
http://www.identityarchives.com