The trail network in and around Traverse City is just about the best you can get for in-line skating, hiking and biking.  And it's getting better all the time.  Plans are proceeding to connect all the individual trails into one massive network.  One of the best trails for all three activities is the Traverse Area Recreational Trail (TART).  A good starting point is the TBA Career Tech Center on Parsons Road.  From there, you can skate, hike, or bike to your heart's content on a paved trail, then on a boardwalk through marshy lands out to Acme and back.  It's about an eight-mile round trip, and some of the restaurants along the way even put out water for travelers.  The Leelanau Trail begins at Carter Road in Greilickville and ends at Suttons Bay.  Only the first six miles are paved, however, so pack some hiking boots or rent a mountain bike if you want to go the 15-mile distance from Traverse City to Suttons Bay.  On the east side of town, the Sand Lakes Quiet Area is excellent for hiking or mountain biking.