We subscribe to Organic Lawns for America. They use all organic, nontoxic fertilizers, weed-killers and soil additives. Package prices are based on area of your lawn, and they send everything right to your door. We have been pretty happy with it so far. The people there are very helpful. They will give you a free lawn analysis if you send them a few pictures and will provide helpful answers anytime. Treatments arrive UPS and they are each shipped so that they arrive at the correct time for application. The fertilizer they use is a treatment of corn gluten meal. It is not as fast acting as the nitrogen overdose that comes with Scott' fertilizer or a truck-based chemical spray-down, but will last longer and your dog can follow you around while you apply it. (Ours likes to bark at the spreader :) Corn gluten is a slow-release source of nitrogen and our lawn is nice and green a week or so after application.
Organic Lawns for America website: www.organiclawnsforamerica.com/
NaturaLawn is a company that does lawn applications and their website says that they minimize the use of harmful chemicals. That said, they do still use them, just in smaller amounts in coordination with some greener techniques.
www.richsoil.com/lawn-care.jsp has a lot of useful organic lawn care tips also.