When I'm in a good mood, I save my dishwater (pareve and milchik only; no meat grease, yuck!) and give it to the garden?
Did it last summer, too.
Just reading the book Sleeping Naked Is Green: How an Eco-Cynic Unplugged Her Fridge, Sold Her Car, and Found Love in 366 Days, in which the author, Vanessa Farquharson, takes on one new "green committment" each day for a year. (supposedly, she's, an eco-cynic, but by that, maybe she means she shaves her legs, because in almost every way she seems suspiciously receptive to the "green" message)
Anyway, the big challenge of the book was thinking up a do-able green step for every single day of the year. She was blogging as she went along, so she had help from readers.
But anyway, I don't remember seeing anything about dishwater. So there! I'm waaaaay ahead of you, baby!