Here's an example of an idea I had just yesterday: A dating site that's like a mashup of meetup.com and match.com with a dash of speed dating. Instead of looking for one-on-one dates, you put in all of your interests and create small groups to do activities together, and then you can get to know each other in person, and maybe click with someone you like. There's no pressure...if you don't connect with anyone, you can at least have a good time hanging out in a group.
Ok, I put my idea out there for anyone to steal...let's see how long it takes for someone to execute it!