In the Birmingham area, Oak Mountain State Park is a good area for trail running. The primary function of the trails, however, is for regular hiking and mountain biking so caution needs to be taken when using the trails.
The following is a link to the Oak Mountain State Park web site, http://www.bham.net/ once at this site select Recreation, then Oak Mountain State Park.
This should provide extensive information on the parks resources, as well as
directions. The cost for park entrance as of 06/15/98 is $1.00 per person.