This is a cute bit of science. Every weekend I get this 20 pound lump of flyers, and today I noticed all the 'green lawn' ads. They are touting Sarritor as the be-all and end-all of lawn weeds. Sounds too good to be true, so I investigated.
This is a brand new product, discovered at McGill. It's fungus which selectively feeds on dandelions, and nothing else. It's no good for all those other things killing your lawn. I'd go out to buy some, but all the available product has been snatched up by the lawn care companies.
Doesn't sound that great, unless you have a heavy infestation of dandelions. Maybe when they have lots of product next year, it will be interesting to try out.