This is for everybody... Like it says, what Openware.. Gimp, etc. do YOU use? One other question: If you could ask any of the guys who work on this  stuff, what would you say?  Lou.

Wings3D, Arbaro, POVTree. I use a lot of other freeware that isn't "open-source" per se, such as MapZone ( great texture making app) UVMapper basic, Ivy Generator, Deep Paint, etc. I would love to see a freeware app, open-source or otherwise that would generate animated "wave" or fluid, greyscale heightmaps in AVI or QT format that could be used in Carrara's displacement channel. Several commercial apps for water simulation use this method, but no freeware apps so far as I'm aware. 
   I have had pretty good success animating terrains in Bryce5 by importing a series of "wave" heightmaps prepared in PS and letting Bryce do the tweening and then rendering the result as an altitude mask movie from top camera view, This does generate a greyscale animation that is usable for displacement, but having an app devoted to this would help workflow on the occasions when animated water is needed. When I'm able to upgrade to C6 the new "Ocean Primitive" may make this a moot point. I haven't been able to try it yet, so I don't know.
                                                                                                                               Cheers, Dan.

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

Thank you for the link Kathye. I'll be sure to check it out. :-) Thank you also for reminding me about Context Free, I've found a lot of uses for it. Another very useful bit of freeware is the "Cumulus" PS plug-in from Flaming Pear. It's not on their site and I got it from AgentSmith from the Bryce Forum. I've used it for a lot of cloud backgrounds and for smoke in my postworking. I've just started getting the hang of Carrara's particles and Cumulus can make some excellent "splats" for smoke particles.

After tinkering a little with Gradient Designer and realising I just couldn't figure out what it was doing with the different blend modes I searched on XOR pen and came up with an even better freeware (perhaps) or at least more usable for me in that it has tutorials so I can start to figure out what to do. It seems to allow for a lot of functions within the software including filters and sinewaves of different frequencies.

It's called sTile at

http://www.harmware.net/index.htm

They're not animators obviously so I'm not sure how well they'd work for your purpose, I'm not an animator either (yet, who knows, Carrara may change that ;) but thought I'd pass it over on the offchance it might have some use to somebody.  It's certainly entertained me for the last hour or two :D

How are POVTree and Arbaro run?

Both use Java to run.

I wrote up a short intro to using POVtree in the Bryce forum a couple of years ago

http://www.renderosity.com/mod/forumpro/showthread.php?message_id=2234245&ebot_calc_page#message_2234245

Arboro is easier to use in that you export the obj direct without needing to go through PoseRay.  Neither of them really has a manual as such so you really have to just use trial and error, Danamo stuck at it longer than I did I think and got some good trees.  I gave up and bought Xfrog ;)

One of the best programs similar to PS or Gimp and I think more powerful is  the free Paint.net program which has loads of effects plugins and has a large community.  The program is updated almost monthly

www.getpaint.net/screenshots.html

Cheers

For 3d I use
Roadkill (pelt mapping UV software - amazing that it is free), deep paint 2d, gimp occasionally but have fireworks

That is about it for free 3d

But I also use open office, and scribus and inkscape, and a bunch of crap everyday from giveawayoftheday.com

i use blender as opensource proggy. great animation and uv capabillities. also a vast renderer and free ;)
here are some tests  modeled rigged and animated in blender.
http://www.youtube.com/results?search_query=ysvry

Attached Link: http://www.brick.com/md/index.htm

I forgot an excellent free app provided by Acme Brick Co.  The Acme Brick Masonry Designer lets you design realistic brick designs using dozens of different colors of brick and mortar. There are several brick and block designs and you can use different course designs. You can mix different colors and blocks together to make special designs. Anyone interested in architecture might find this cool little app very useful. When you are done making your design you can save it as a bitmap and a matching bump is also generated. Highly recommended!

Free apps I  use - Wings3D, MOI (beta - Moment of Inspiration), Gimp, VirtualDub, UV Mapper Classic. I want to learn Blender3D but find it's interface too hard to grasp...

"I want to learn Blender3D but find it's interface too hard to grasp..."- I hear you on that one. Blender shows its non-Windows origins in its interface, but it has some excellent capabilities, some of which Carrara can't touch yet such as fluid simulation. I heard that an upcoming ver. may have a more "user-friendly" interface, so I plan to keep trying it. Maybe it will eventually sink in,lol. Ysvry figured it out and does some great stuff with it.