Lately most of my time is spent doing landscape stuff with Vue and World Machine. I also use Terragen 4 but not so much.It was the free version of Terragen that got me going on terrain stuff. I still keep Lightwave up to date but have not used it much of late.
In the past I used Real 3D, Imagine on the Amiga and Bryce and going back further Vista Pro. See side menu for some of these.
Below are a few of my terrain animations .