Butler-Freeport trial is a nice rails to trails project that runs almost all the way into Butler.  There is a good access point by the Summit Township building.  For the best scenery head south from there.  There are historical signs along the trail that tell the tail of the old railroad and the area.  They're a nice touch.  The trail goes through mostly woods, farm and golf course for the portion in the north; Very scenic.

Moraine State Park also has some great trails.  There is a paved bike/walk way that runs along the lake.  This one is great with the kids.  For a long hike there is a trail that connects Moraine with Jennings Nature area.

Jennings has several shorter easier trails.  There are some unique portions and the meadow is wonderful.  This trail has signs that talk about the environment of the area. 

McConnel's Mill has a couple of great trails.  The trail through the gorge is beautiful and a good choice if you're hiking on a hot day.  Because its in a gorge that is lined with tress there is a lot of shade.  The water also keeps the area cooler.  It can't be beat for beauty in the fall.  The first part of the trail near the Mill is easy, but it gets more difficult further downstream.