In Google Docs, is there any way to find out exactly when a document was shared with somebody that I created and shared? This would be useful, at least for me, in finding out exactly when a document was turned in.
If you are trying to find out when you shared a document with other people, AND you notified the recipient by email, then you can search Gmail for your message.
In Gmail, search
From:me <title of document> and it should pull back the email that was sent to the recipient. Body of the message starts with "I've shared an item with you"
If you shared a document with someone but suppressed the email notification, then I don't think there is a way to determine when it was sent.