Metacreations Bryce is an interesting 3D terrain-generating application. You can build some beautiful landscapes, create animations, and even import 3D models from other programs.
The Forest is another quick and easy landscape using a "mountain" to create a simple model -- in this case, a forest full of trees. Experiment with different textures (trunk, terrain, etc.) to get...
The River Valley is one of my favorite Bryce landscapes for two reasons:
1.) It amazes me how much you can do with a simple mountain.
2.) Simple changes (like the angle, textures, and sky) make a huge difference in how it looks.
Creating a desert in Bryce is more difficult because you can't rely on your water to make your scene look cool. We like to work with camera angles, haze, sun/sky settings, and textures to make my scenes really pop. Experiment and have fun!