Every once in a while I see someone asking for sources on digital, participatory, social media projects around museums, public history, social history, etc but I don't always have a moment to reply. To make it easier to help people, here's a quick collection of good places to get started.
I think the best source for museums and digital/social media projects is the site and community around the Museums and the Web conference, including 'Best of the Web' nominations and awards (2012-1997) and conference proceedings: 2012, 2011, 2010-1987.
Other projects might be listed at the new Digital Humanities Awards (nominations closed on the 11th so presumably they'll publish the list of nominees soon) or the (US) National Council on Public History Awards. The Digital Humanities conferences also include some social history, public history and participatory projects e.g. DH2012, as did the first Digital Humanities Australasia conference and the MCG's UK Museums on the Web conference reports.
To start finding online communities, look for people tweeting with #dhist, #digitalhumanities, #lodlam, #drinkingaboutmuseums, #musetech (and variations) or join the Museums Computer Group or the Museum Computer Network lists (or check their archives).
I'd like to add a list of museum bloggers (whether they focus on social media, technology, education, exhibition design, audience research, etc) but don't know of any comprehensive, up-to-date lists (or delicious etc tags). (Though since I originally posted @gretchjenn pointed me to the new 'Meet a museum blogger' series and @alexandrematos told me about Cultural blogging in Europe which includes a map of the European cultural blogging scene.) Where do you look for museum bloggers?
This is only a start, so please chip in! Add any resources I'm missing in the comments below, or tweet @mia_out.