StackOverflow has served as very well in the past couple of months with the Blue Obelisk Exchange. The BOx was taking advantage of a beta project of StackOverflow, and users of that program can switch to a payed plan after the beta phase was over. That moment is nearing, but the pricing model is just unrealistic for us. There were also some comments on the Blue Obelisk using proprietary software (see Stackoverflow not open source — not a problem?).
To address both issues, and with the help from the Shapado.com developers, I have moved the (CC0) data to the the new host, http://blueobelisk.shapado.com/. I got a report today that there were some accounts mixed up (affecting four accounts), but that seems to be resolved now. The Shapado software has an OpenSource license (AGPL), and the code can be downloaded at Gitorious. The new questions page looks like: