Free is great and in a state that many parks charge a fee, even if you walk in, it can be tough to find. Marshall Hampton Reserve is one of those great free hikes. It is open year round from about 6 am to 6 pm depending on the season. It is open to hiking and horseback riding. Although you may need a special permit to horseback ride. You can contact the Polk County Environmental Land Program for information about permits for horses. As of Oct. 1, 2013 their phone number was (863) 534-7377 and permits were free. There are two trails, a 3 miles loop and a 2 mile loop so you can do a 5 mile workout easily.
The reserve parking is at the intersection of Thomhill Road and Winter Lake Road in Polk County near Lake Hancock.
Osprey Overlook loop trail goes around a lake and is predominantly dirt with no vegetation. Imagine walking on a lake berm. It gets very muddy after rains so it is critical to wear shoes you don't mind getting dirty. It is not uncommon to see alligators, osprey, or eagles below the berm on the pond edge. This loop is approximately 2.5 miles. There is virtually no shade on the trail.
The Acorn Hammock Loop is approximately 3.5 miles. It leads you away from the lack and into the oak forest land. It meanders through woodlands and is predominantly shaded. It can be wet, but there are several areas with wood "bridges" so you can still hike during the wet season. It is not uncommon to see black boar and birds along the trail.