A week or two ago I launched http://demoseen.com/webglenabler/ to enable WebGL on iOS devices. In theory, it's profitable -- it cost me nothing (outside of a few hours of dev, which I spent on myself anyway) and has made a whopping $26 or so -- but it'll never really go above that, and 'sales' have already stagnated. It was interesting to see the breakdown of downloads versus payment, and how much people paid. I also wonder how much I would've made if I put it up for, say, $1 only.

Edit: Also interesting that it got quite a bit of attention on HN and several hundred (maybe 400?) downloads and not a single sale (from what I could tell). That surprised me a bit; every sale has been driven by people coming from tweets that some big names in the jailbreaking scene retweeted.