Butler Fork is an amazing single track trail that has access to several other areas in the Wasatch, making it the perfect trail for a great mountain adventure.
To get to the trailhead, drive up Big Cottonwood Canyon 8 miles. The parking lot is on the left side of the road. The first half mile is the steepest of the whole trail so don't get too intimidated by it, it mellows out a lot after. You will come to fork in the trail about a mile in, you can either take the left trail towards Mill A Basin and head through some amazing aspen switchbacks, or take it right towards the Dog Lake connector trail. Both trails eventually meet up with each other and make a 7.2 mile loop.
The trail is perfect for a good solid trail run because its elevation gain, flat, and descend are all pretty even. The views are fantastic, so make sure to stop and soak it all in.