Picked up a Specialized Stumpjumper 29er frame on ebay that has a pretty cool sliding dropout design.  Have been running it geared, but toying with the SS idea.  After a couple of rides where I've picked a gear and just left it there, I can say riding SS is a tough workout!  Really makes you think about maintaining speed and getting up the climbs with some momentum.  Fun stuff.

let's see some photos.

Skip the SS coasty and go fixed!  You'll never go back.............

Haven't had a chance to take pics, but found a few online.  The frame comes with a driveside dropout with a hanger and one without for SS.  The allen bolts clamp down on the pieces pretty firmly and the backs of the parts are knurled to make em grip.  I've been running it all the way forward to shorten the stays when running gears.