Really? Huffington Post is the most leftist/socialist site on the planet? Maybe in the eyes of Fox News viewers. Arianna Huffington herself (http://en.wikipedia.org/wiki/Arianna_Huffington) is very, very far from being affiliated with socialism.

Here are a few (well worth reading) sites that are actually closer to your description:

http://www.zcommunications.org/znet

http://monthlyreview.org/

http://links.org.au/