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.
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...
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 Island is probably the most common and most basic landscape that you can create in Bryce. We like to take it a step further and edit the mountain a bit for more realism.