As we mark the 12th anniversary of the September 11th attacks we recommend taking a look at the September 11 Digital Archive created by the Center for History and New Media and American Social History Project/Center for Media and Learning. It is one of the earliest examples of an online collecting project that used contributions from the general public, or crowdsourcing, to build its archive.
The description from the site:
The September 11 Digital Archive uses electronic media to collect, preserve, and present the history of September 11, 2001 and its aftermath. The Archive contains more than 150,000 digital items, a tally that includes more than 40,000 emails and other electronic communications, more than 40,000 first-hand stories, and more than 15,000 digital images.