One I'd recommend is Mingo Falls. It's a bit difficult to find the entrance to the trail (small country roads & few signs), but once you arrive, you'll note that there's less than a dozen parking spots and there's still room for your car (especially small crowds if during the week). Once at the Mingo Falls Campground on the Cherokee Indian Reservation, you only need to hike 0.4 miles. It's considered moderately difficult because it includes 161 rough steps built along a creek, sometimes wet and muddy. But when you get to the top, it's worth it. Watch 120 ft. of water cascading down while standing on bridge. Hear the peace. Smell the fresh air. Feel the breeze.
There's many waterfalls near the Smoky Mountains, here's 8 more to add to your "to see" list:
1. Mingo Falls (as pictured above)
2. Juney Whank Falls- moderate 0.8 trail to 90 ft. falls, from Bryson City drive to Deep Creek Campground
3. Abrams Falls - moderate 5 mile hike to a 20 ft. waterfall, short but powerful with its large volume of water, near stop #10 Cades Cove
4. Ramsey Cascades - difficult 8 miles, but rewarding with the park's tallest waterfall (100 ft), 4.7 mile drive first from the Greenbrier entrance (TN)
5. Meigs Falls - 0 hike, drive along Little River Rd and stop at the pulloff 13 miles west of Sugarlands Visitor Center (TN)
6. Hen Wallow Falls - moderate 4.4 mile hike from Gabes Mountain Trail, park at Cosby Picnic area
7. Indian Creek/Tom Branch Falls - easy 1.6 mile hike, 2 falls for 1 hike special, Indian Creek Falls = 25 ft. tall, also from Deep Creek Campground
8. Mouse Creek Falls - moderate 4 milke hike, includes Midnight Hole, a picturesque pool below a 6' falls; exit I-40 at Waterville Rd. (#451) turn left after crossing the Pigeon River and proceed 2.3 miles
Tip: See photos before the trip to choose which one you want to visit. I've added a photo gallery of each of the 8 falls on flickr for you http://www.flickr.com/photos/krenda/galleries/
