Right, let's kick this thing off again - the Terragen Renders thread on the old forum was the best thing about the gallery.
For those that don't know, Terragen
is a free 3D scenery generator and renderer for Windows and Mac. Like all the best things it takes seconds (well maybe an hour) to learn and years to master. Follow the above link to download the tiny application yourself and see how you go.
Here are some of mine to get us started: