This trail is probably the most well known mountain bike trail in the country. That being said, it is not necessarily the BEST trail in the country. It is definitely unique due to the tread (rock) and the desolate landscape that surrounds the area. The trail is full of short steep climbs and descents and will really work your legs out. Plan on taking a few hours (3-4) to ride the loop all the way around. If you plan on hitting this trail in the summer (like we foolishly did), be sure to get there real early before it starts getting unbearably hot. Don't even think of trying to do this trail in the evening because it will still be just as hot (due to the enormous heat capacity of the rocks). Again, the trail is unique and is perfect for mountain bikers looking for a trail that is totally different from anywhere else they have ridden.
From town, take 400 West off of Main Street. Turn right onto Mill Creek Rd. Go straight through the stopsign and follow the signs to Slickrock. There is a pay station as you enter the BLM area. Right now it costs $5 per car or $2 if you're on a bike (although I wouldn't advise riding to the trail - the road is pretty much uphill the whole way out of town).
http://www.singletracks.com/item.php?c=1&i=511