Congaree National Park offers a variety of hiking, camping, and backpacking activities.  By combining multiple trails, you can make your trip as long or short as you like.  Multiple camping areas are available including the after hours campground, the primitive Bluff campsite, and backcountry camping.  A free permit is required for all camping, which can be obtained at the Harry Hampton Visitor Center.  The park is usually very busy on the weekends and in the summer, so plan your trip during non-peak times if possible.  Also, since the area is a swamp, the summer months will bring the largest mosquitoes around so bring plenty of bug spray to make the trip more enjoyable.  The River Trail is a great hike with not very much activity (except the wild hogs).  With that being said, the trail is not well maintained on a regular basis and will require finding new paths around fallen trees and rising swamp waters.  Make sure to bring your compass and make this trail a moderate 1 day hike, or an easy 2 day backpack.