Using Web 2.0 sites to promote your own site

If you have not been to any of the web 2.0 sites you should check them out. They are a great way to increase your rankings with search engines like google. Below are a few of the sites that are free to sign up on and you can write comments and links to your site with:

http://twitter.com/
http://del.icio.us/
http://technorati.com
http://digg.com
http://stumbleupon.com

I will post some more later.