Social bookmarking sites are also a popular way for bloggers to promote their blogs and gain more traffic.  Social bookmarking sites can also be used to increase the number of other blogs and sites that link to your own blog.  This linking can increase traffic and, if the sites linking to you are quality sites, PageRank.  Some popular social bookmarking sites are:

Blink List:  <http://www.blinklist.com>
Blog Marks:  <http://www.blogmarks.net>
Bloglines: <http://www.bloglines.com>
Bookmark Sync:  <http://bookmarksync.com>
De.Lirio.Us: <http://de.lirio.us>
Del.Icio.Us:  <http://del.icio.us>
Diigo: <http://www.diigo.com>
Digg:  <http://www.digg.com>
Fark: <http://www.fark.com>
Faves:  <http://faves.com/friends/dots>
Feed Marker:  <http://www.feedmarker.com>
Feed Me Links:  <http://feedmelinks.com/portal>
Furl:  <http://www.furl.net>
Jump Tags:  <http://www.jumptags.com>
Link Roll:  <http://www.linkroll.com>
Mister Wong: <http://www.mister-wong.com>
Mixx: <http://www.mixx.com>
My Web:  <http://myweb2.search.yahoo.com>
Reddit:  <http://reddit.com>
Simpy: <http://www.simpy.com>
Slashdot: <http://www.slashdot.org>
Sphinn: <http://www.sphinn.com>
Stumble Upon:  <http://www.stumbleupon.com>