One of the key topics I'm interested in: what impact do museum websites have? Do users/visitors do anything as a result of their interactions that has an observable effect in the world? If we were to check in with them a month or two later, would we notice any difference for their interactions?
A small group of us broke out for one of the "unconference sessions" to explore the issue. An interesting topic that came up: options for "micro-participation" -- from quick payments for relief efforts in Haiti via texting, to pothole reporting systems facilitated by mobile phone in Boston. Ease of participation is key.
A couple websites on the "Best of the Web" list, for which I was one of the judges, come to mind as well: Solar Stormwatch, by the Royal Observatory in Greenwich, which trains volunteers to make observations within visual data too subjective for individual users to make. Space weather forecasts are generated, and solar storms identified before they reach earth. Another site that caught my attention: Meet Me, the MoMA Alzheimer's project, which is inspiring for the way rises to the occasion to be of service to a specific need in its community.