MTB trails in the area

Here a collection of MTB trails, please post comments with your favorite trails. Thanks.

Harmony Hill Nature Area:
Set up by the MTB enthusiasts for the West Chester Cycling Club.
Directions from West Chester to the Skelp Level Road parking area:
Take Route 322 west towards Downingtown. Make a right on Skelp Level Road (PECO substation will be on your left). Go approximately 0.8 miles to the intersection of Harmony Hill Road. Continue straight on Skelp Level Road. You will pass Overhill Drive and Winchester Trail on the left; the next left – 1200 Skelp Level Road – is the parking area. If you reach Wilderness Trail, you went a little too far.
http://www.eastbradford.org/specialinterest/Sonoco/Sonocoindex.htm
Trail maps: http://www.eastbradford.org/specialinterest/Sonoco/HHNATrailsMap_061708.pdf

Valley Forge: Betzwood
Directions: Take the Trooper exit off of Rt 422 and enter Valley Forge Park. The Betzwood parking lot is on the east side of the Schulkyll river. Trails start at the end of the Parking lot.

Wisahickon Park
20 miles of trails within Philly city limits...
The multi-use flat trail that runs the length of the park provides access to the many trails that climb out of the valley. The trails are well marked and not all trails allow mountain bikes. The trails are primarily intermediate to expert and have plenty of both up and down hill sections. This is not really a trail for beginners, but a beginner can always walk the more difficult areas. There are some sweet single-track areas, rock gardens, logs, jumps... Overall this is one of the best Trails in the Philadelpha area.
You may need an annual park pass to ride.
http://www.dirtworld.com/trails/trail.asp?id=438&trail_name=The%20Wissahickon%20Park%20Mountain%20Bike%20Trail

Marsh Creek State Park
Variety of scenery on the trails is amazing. Within a mile you will hit large deep mud puddles, rocks, fields with tall grass, dirt paths in open woods, etc.
Directions: North on Rt 100 in Exton. Follow signs off of Park Rd.
http://www.dirtworld.com/trails/trail.asp?id=13310&trail_name=Marsh%20Creek%20State%20Park%20Mountain%20Bike%20Trail

French Creek State Park
Loads of technical single track. Trails are filled with Rocks and long steep climbs. Pick up a map at the park office.
Directions: Take exit 23 from the PA Turnpike.
http://www.dirtworld.com/trails/trail.asp?id=440&trail_name=French%20Creek%20State%20Park%20Mountain%20Bike%20Trail

White Clay Creek State Park & Middle Run, Delaware
30+ miles of twisting trails
http://www.kencox.net/?page_id=29