North Sand Hills
The area has a network of challenging trails just north of the dunes. It is a long trek from the Front Range, but definitely worth it. You will find a lot of different options for camping, and it is a very popular area on weekends. Watch for postings of closed areas, bring your own firewood and pack out your trash.
Take Highway 14 west from Fort Collins through Poudre Canyon. At Walden, head north on 125. About a mile north of Cowdrey, turn right on C.R. 6. Head east 3.3 miles and bear right on BLM Road 2509. After another 1.5 miles, bear left to main camping area near Toilet #1. (Right here goes to alternate starting point nearer the dunes.) Total distance from Fort Collins is about 115 miles. See Trail #2 for a fun back way into the dunes.