The source and host for all these pictures. Get a supported blog and a free flickr account (yahoo logins work) and start your own found flickr photo site.
Occasionally features pictures found by flickrgirls, but also links to other found flickr picture, which can be more posed and professional. Contains prominent links to non-SFW sites.
Mostly SFW, but there's some Maxim-grade pictures.
There're a few others out there in the non-SFW category, but I'd rather not promote them.
del.icio.us page Add this site to your del.icio.us bookmarks, and see who else has it bookmarked.
Also there's flickrgirls on technorati. Links found on both of these pages may not be SFW.