There is. I'm working on this through the Labor Party (www.justhealthcare.org), but it's unlikely there's an active chapter in your area. Most states have some kind of effort going, with California the most advanced I know of (California Nurses Association/NNOC, a Labor Party affiliate, is in the lead on this). The big national single-payer coalition is Healthcare NOW (http://www.healthcare-now.org/) --god they need a web designer, it's a jarring mess over there. The 'contacts' tab has a map to hook people up with a local effort.
Most of us are pushing HR676 (Conyers' bill), which has maybe 90 co-sponsors in the House. There is a significant movement within unions to support this bill, with around 27 state AFL-CIO's (now including CA) and a zillion locals and central labor bodies signed on. That is being kept track of, and pushed, by Kentucky-based All Unions Committee For Single Payer Health Care. Of course, there's also Physicians for a National Health Program, which has great ammo on their site, pnhp.org, including critiques of HRC and BHO's plans, if anyone wants to read what people who've been working on this issue for 3 decades think of the current candidates' claims to 'universality.'
SickoCure.org is a site PNHP set up following the release of Moore's film. They have ads that the California Nurses Association made to criticize the Dem. candidates. Lots of fliers to download. Nice site. CNA has www.guaranteedhealthcare.org
Jenny Brown