CiteULike (articles)
Connotea (articles)
Flickr (images)
FreeGovInfo (EPA government documents)
LibraryThing (books)
PennTags (library catalog records)
Podcast.com (podcasts)
ScribD (documents)
Slideshare (powerpoint presentations)
YouTube (video)
Do you have some other favorite sites? Let your fellow participants know by adding a comment to this post!