Trail between Breck and Frisco (peaks trail?) is a great one, mostly downhill from Breck but you can ride back on the bike path if your inclined, wife and I have done the out and back from Frisco a few times, great fun.
The Peaks Trail is a fun trail, either as an out and back from Frisco to Breck, or as a loop with the paved bike path for a return route. Wilderness Sports on Main St. in Frisco is a decent bike shop, Breck has a couple of options (Racer's Edge, Great Adventure Sports, a few others).
Along with the free guide, there's at least one guidebook to Summit County and there are topo maps that show mountain bike trails, all available at bike shops and outdoor shops.
High Trail Sports, right across from the Holiday Inn in Frisco was amazing when we went out there for Ride the Rockies. Small selection of bikes, but a great guy behind the counter, and I told him I would spread the word.