[EDIT JAN-06-2007]
I have made some progress on an app using these blocks, has a lot of promise. Source code and win32 distro can be found here:
[link]
Have fun!

This is a set of isometric blocks, and can be taken at face value. However, if you inspect it a little, you'll find some interesting things that I painstakingly wrought into this beast:

1) All blocks have very specific dimensions, and line up perfectly when you put them together.
2) Each prime side of a block measures either one or two units of length - this lends itself to building.
3) Lego style, I've created a number of interesting models using these blocks, but I don't think it's worth posting them.

For my target audience, the people who will look at this and immediately want to fiddle around with the blocks and build stuff right away, I have a Paint Shop Pro 7 format layered file that makes it extremely easy to copy/paste into the provided area and build structures and what not.

Realizing that this system works poorly at best for the average viewer, I've begun work on a Flash version of this, an interactive builder. Due to my relative inexperience with actionscript and its quirks, I've not been able to get this version to work to my satisfaction.

The ideal outcome is a flash program where you can drag and drop a number of blocks into the workspace, and that they would be aligned to an isometric grid, to facilitate easier building. I've got most of the actionscript for this done, minus the grid, and also there's an annoying quirk that I can't seem to change the depth on programmatically-created instances of my blocks, so I can't bring the most recently dragged block into the forefront of the stage, like one expects intuitively. Oh well.

So I decided just to show you all this, and to show my watchers that I'm not quite dead.

[Edit: September 22, 2004] I tweaked the shading on the angled blocks so that when they are put together, they create a more believable sense of dimension than before.