Share and share alike (not)

Hmm...how to choose among so many great tools to share data?

Sharing bookmarks
http://del.icio.us/

Sharing documents (and collaborative authoring)
http://www.writely.com/

Sharing to-dos
http://www.backpackit.com/

Sharing thoughts
http://www.blogger.com/

Sharing photos
http://www.flickr.com/