Adsense. With only about 10k hits a day, my bedtime
calculator http://sleepyti.me brings in $10-$20/day. At the rate you're getting users, you could probably bring in a significant load of cash. Good luck!
I don't know if you read the "Sacked by a Google Algorithm" article from yesterday. http://www.duckworksmagazine.com/11/columns/guest/winter/ind... The comment you make on the results page sounds dangerously close to what got Adsense to boot him.
A few people have posted my URL to social news sites like Reddit and Digg, but even when those gain traction it's usually just a few thousand and quite short-lived.