Do you have a 3D printer? Are you running it as often as you can? Would you like to make some money while between interesting prints? Why not rent out your print time to others?
Then ProtoExchange is the site for you. Only, it needs your help to get started, so visit the Indiegogo campaign and donate to the developers to get ProtoExchange up and running.
This is an idea that I've advocated we've needed for a while. I'm glad to see someone finally making it happen. Personally I would have take a bit off the top, after all eBay, Etsy, and everyone else does and no one bats and eye. But these folks seem determined not to and I respect that.
So head on over to Indiegog and support ProtoExchange.