Stinging Nettle, Urtica dioica, a quick search tells us it's full of good stuff plants love: Nettle is rich in chlorophyll, and a good source of beta carotene; vitamins A, C, and E; tannins; iron; calcium; phosphates; and various other minerals, especially silica.
For the most part it seems the traditional method, used for ages in england & france, is to let it sit in water for 10 to 15 days and it will stink to high heaven.
I'll be picking some up and using it the same as i do my alfalfa which i have excellent results by just adding a small scoop into my compost tea & letting it bubble for about a day. Nettle doesn't grow where i'm at, maybe it's the elevation and the long winter season, but i found lots of dried organic herbs/plants at mountain rose herbs website that i'll be trying out.
Here's a link with a detailed description of how to make it, french style.
http://www.frenchgardening.com/tech.html?pid=309088884143