The “Covered Bridge Capital of New Hampshire” is the little town of Swanzey, just south of Keene [1]. The town boasts five bridges over the twisting Ashuelot River. The 136-foot West Swanzey Bridge (Main St. and Rte. 10) is a brick-red beauty, with an attached pedestrian walkway on one side.
The 158-foot Cresson Bridge (Sawyers Crossing Rd.), which is still open to traffic, is known for the intricate latticework on its inside. You can visit all of the bridges on a covered bridge biking or driving tour; inquire at the local Chamber of Commerce.
Links:
[1] http://www.moon.com/destinations/new-england/new-hampshire/south-and-seacoast/monadnock-area/keene