In the September 2011 UK Scriptwriters podcast, Tim and I discuss dialogue: the good, the bad and the exposition. I got this follow up Q, which might be of interest:
"If you are creating dialogue that reflects a crowd's uttering and you want the speakers to be heard but not seen can you put them under a title of 'Various' and how do you separate each speaker in the dialogue text?"
Yes, you could put 'Various', that would work, something like:
Or you could put 'Crowd' instead of 'Various'. Or space out each line to an individual crowd member:
As long as it's clear and doesn't disrupt the story, or the reader's understanding of what's happening, then you should be fine.