Seems that the trend of late is to have a short film made about gravel grinders. Trans Iowa has one out, but it is only in private distribution as of now and not public. (Here is the trailer for it though) The Dirty Kanza also has had several amateur films made about it. The Gravel Metric has made a few great promotional shorts for their event as well.
However; now folks are actually making produced, finely crafted films in the public domain concerning gravel grinding. Here are a couple we're aware of right now.
The first isn't out yet, but soon should be. it is going to be based on the recent running of the Heck Of The North. Here's a sneak peek:
The other one that has been making the rounds is about the Almanzo 100. This one was produced by Royal Antler Films:
If you know of anymore, pass them along and we'll make folks aware of them here.
Updated- 10/5/12: Here's an excellent film about D2R2 Click Here