Social Bookmark sites can boost traffic to your webiste free especially if if you bookmark a video
you have submitted to youtube etc
Here are my Top 10 List of Social Bookmark sites that I know boosts traffic
www.digg.com
www.del.icio.us
www.StumbleUpon.com
www.reddit.com
www.MyBlogLog.com
www.blinklist.com
www.newsvine.com
www.mister-wong.com
www.furl.net
www.technorati.com
Hope this helps
Matt