Aside from MMD, there are all sorts of tools available to enhance your animations or speed up production. Some are there to enhance your display, but produce amazing results!
This allows you to create a crowd, or a 'mob' or models within MMD. They're all controlled by the same motion data, and use only one model file, thus it doesn't slow your system down as much as loading models one at a time. There also seems to be some dummy models available for download. MMD version 706 or higher is required.
Here's a quick tutorial by Selfishneko to walk you through the basics.
PMCA Mob Assembler
PMCA now has it's own information page. Click here.
Just a simple tool for creating characters intended to be used with MikuMiku Mob. The idea is to create subtle variations in a bunch of clones to use in the background. It comes with a couple of sample characters, textures, and model parts for you to use, it's kind of like a scaled down 3D Custom Girl (But WORK SAFE!!! =D).
The download is given in the Nico video at the top of the post.
I really don't know alot about this one yet, aside from the fact that it can create a split screen, or be used to give your videos a Stereoscopic
effect. If you own the right glasses, you may be able to create and
watch MMD, in 3D. This only requires the standard Red & Blue glasses, not the expensive ones. Here's a demo
of the 3D technology in action.
Paperguitar.com seems to be adding some nice goodies lately. This is one of them. You can preview .x accessories before ever loading them into MMD. Unlike most MMD stuff, there is an installer. Might take some time to finish, assuming mine isn't just hanging. You could use this just to preview any .x file really. On the left of the program you're given a folder hierarchy, and on the right is the preview. Right click and drag to rotate around the model, use the scroll wheel to zoom.
MikuMiku Effect now has it's own information page. Click here.
Recently released, MikuMiku Effect is
capable of using rendermonkey presets. In order to make your own, you'd
have to download the rendermonkey 3D program. When you download MME,
(the first link given in the NND video description) extract the contents
into your root MMD folder. Open MMD normally.
Some users have
reported getting errors or having it crash on them, myself, I get a
dialog warning me that just-in-time debugging is not enabled, but I
suspect this was a prior issue. You may need to update your .Net
framework. This is unconfirmed.
Simple Particle Editor
This is a tool for editing particle effects. You need at least
.Net Framework 3.0 to run it, and in order to view the effects you of course need to have MikuMiku Effect up and running.
Diffusion Filter Editor
This'll let you create a diffuse (soft glow) effect. You'll need to scroll down until you see the example picture (mermaid chibi Miku).