Modelling
Dumped:
For general unwrapping, this script is amazing. Align tools, rotations, mirrors, and plenty more and it's only a script, not even a plugin.
http://fearthedevil.com/words/?p=117
I use unwrella for any organic based model, it's quality and process time is just ridiculous. Pelt seems take like 5 minutes to set up, and maybe another 5 minutes to tune them for unwrella to do the unwrap properly. The map's literally have no proportion errors and all the checker patterns line up seamlessly.
http://www.unwrella.com/
For rendering UV maps, I use textporter. I feel like most people somehow don't have this, even though I think it's the most essential plugin you should have.
http://www.cuneytozdas.com/software/3dsmax/
Not really workflow related but shaderFX is great if you know HLSL or even used UT3 shader editor. Creates real-time DX shaders which are great for presenting next-gen pieces for portfolio or whatever. Even good to use to create replicant shaders of engines like UT2.5 so you know how your piece will look in-game, but obviously you can do all that in real-time rather than constantly porting to different programs.
http://www.lumonix.net/shaderfx.html
I prefer using this shader though, it's just clutch. Could use some refract/reflect additions and parallax would be nice as well.
http://www.laurenscorijn.com/viewportshader
For a toon orientated shader, here's an amazing one, use it all the time for TF2 stuff(half lambert and what not)
http://blog.maginot.eu/index.php?p=till.1__scriptnstuff_shader_toon
Also, for UV optimization, you should try this out. Possibly the best plugin ever, and as far as I'm concerned it's free. I think you only need a license for commercial use, cause I've had it for months and it still works fine. Packs your UV space for a nice 1:1 pixel to poly ratio, really clean as well.
http://packer.3d-plugin.com/
Some amazing plugins, scripts, and tutorials, including rigging a tank.
http://joleanes.com/
Forums for military modellers.
http://www.military-meshes.com/forums/
Vital to remember when creating textures, is choosing the format that works best for the texture that you are creating, to balance size with quality. (Quality includes not only the palette size, but how much transparency there is.) http://udn.epicgames.com/Two/UnrealTexturing.html
Here is the information that you need to make your decision, and http://udn.epicgames.com/Two/TextureComparison.html
here is a comparison between them. (I'm pretty sure that one of the reasons some DH textures look like utter crap is because they were [i]overly[/i] compressed, with DXT1.)