There is a cool crowdsource library getting organized over at Audible Worlds. Site runner Mike Niederquell’s explanation says it best:
The goal of this library is to capture 3-5 minutes of crowds or walla from your local region. It’s best if the conversations in the recordings are unintelligible, which is why we are using the term “walla” to describe this project. We realize it’s probably unrealistic for most people to have access to a group of performers to capture proper walla, so recording large groups of people in a public area is also being accepted.
Everyone is allowed to contribute and your contribution awards you everyone else’s submitted recordings which from the looks of it will be a *lot* of people! The Submission window is Oct 1, 2014 to Oct 20th, 2014 so there isn’t much time left! Go check it out along with the rest of Audible Worlds. Its a great resource.