I've got quite a lot of utilities for both general work on the computer and for artwork.  I'll try and remember some of them:

Context Free
Easy Thumbnails
Screenprint32
Plant Studio
Universe (an old standalone version)
Arboro
POVTree
MapZone
Wood Workshop

Other essential utilties
Stripfile
Treesize
AVG 
Zonealarm

What would I say?  For the folks that write open source or giveaway freeware it would be a very loud THANK YOU because it amazes me that they are so generous with what to me is a mysterious gift to write software.

Danamo, your comment about wanting greyscale heightfields reminded me of something I have installed but haven't worked out how to use yet.  I have no idea if it would help with what you are needing because I only ever get very regular looking wavemaps out of it but here's teh link anyway

http://www.wolfiesden.com/downloads/images/gradient.asp

Kathy