How about this for a cool Venture:
Princeton Undergraduate Student + Worm Poop = Terracycle = Money.
Tom Szaky dropped out of Princeton to start Terracycle, a company that sells worm poop. It all started by using waste from the university's dining halls, which they developed into liquid fertilizer. The genius of the operation is all the waste is free and you have to worms doing the work.
They also package their fertilizer in recycled soda bottles purchased for five cents each from 3,400 elementary schools and nonprofits holding fundraisers. The nonprofits and schools earn money and Terrcycle get cheap supplies.
Their products are now sold at The Home Depot, Wal-Mart and Target. Initial growth was slow but the four-year-old, 12 employee company projects USD 6 million in sales for 2007.
Terracycle call themselves eco-capitalists - I'd say they're definitely social entrepreneurs. Check them out at www.terracycle.net.