Recently on my blog we had questions about when to return from an injury; one of the injuries was a fractured tailbone. Here is a link to the article, which may be of help: http://www.irunnerblog.com/?p=394.
That happened to me a couple of winters ago -- slipped on ice. My tailbone was sore for about a month. The soreness wasn't great, and I started running after 2 or 3 days of rest. You can probably walk before you run; just do what minimizes the soreness.
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