"Founded in July 2005, Mashable is the world’s largest blog focused exclusively on Web 2.0 and Social Networking news. With more than 5 million monthly pageviews, Mashable is the most prolific blog reviewing new Web sites and services, publishing breaking news on what’s new on the web.

Friendster is a popular social networking site with a large user community. SEO specialists will find it valuable to remix their site content to create a presence for their domain on Friendster. The site has profiles, applications, connections, people pages, photo sharing, videos, fan clubs, and more.

orkut.com is Google's take on social networking, and as such, has swiftly become one of the top sites on the web for building a web presence for SEO. Consider opening a "second branch" of your site on Orkut, and re-mixing web content from your main domain to reach a broader audience.

MySpace is the number one social networking site on the web, and if you are doing a Search Engine Optimization campaign for a web site, you'll want to make sure that you start here. I recommend most web sites set up an account at MySpace, and develop a second site there as part of their web presence. This is a proven way to bring new traffic to your site organically, and to build community.