Some are communists, most are socialists of one sort or another. 

I used to know a man who was a member of the "Socialist Labor Party", an offshoot of Marxism called DeLeonism (basically syndicalism). Just now, I went to the party's website to see how it was doing. They held their last national convention in 2004. There were 43 people in attendance, and the subject of the keynote address was essentially "Our party is not actually dead." This seemed to be nothing more than whistling in the wind. The party is dead to all intents, and the website was last updated in 2010.