Which Web 2.0 Site is best for SEO Link-building?

Which Web 2.0 Site is best for SEO Link-building?

Blogspot, tumblr, weebly, livejournal are the best web 2.0 sites for content promotion and link building.

Now a days wordpress and tumblr works best for web 2.0 creation. Also blogspot is another important site for web 2 creation.