Chagrin:
If you wanted to do heat fusing you could use powder coating powder instead of toner. This can be purchased around $15/lb. and even less in bulk. Any color you want
Never looked at powder coat - is it a plastic (in particular - a thermoset plastic)? For some reason I had it in my mind that it was metal of some sort...
If so - that would pretty nice, especially if it is a fine powder (toner is a very fine powder - and not something you want to inhale); the powder would have to be of a particular granularity to avoid scattering the light too much.
...and color is important here; I specifically mentioned black as it would absorb infra-red/red laser frequencies (as used in DVD burners) best. Other colors could be tried, but white (or other light colors) probably wouldn't work as well (if at all) due to reflection.
Still - this seems like a particularly interesting method/idea that I hope will be followed up on by the DIY 3D printing community (if they aren't already experimenting in this direction). I wish I had the time to try it myself (I'm a one-project-at-a-time guy - no time for this one).
Beyond this - so far the most interesting method of homebrew 3D printing I have seen has been a homemade photopolymerization printer:
Check out the detail that guy is getting! The setup is really simple, too - using only a fine-pitch Z-axis actuator, some kind of "rocker" actuator to "break" the last layer away from the "stage", and a glass "stage" in which a pool of the photopolymer sits, with a high-resolution projector mounted and focused below (his rig could probably go to even higher resolutions if he could procure a black-and-white only projector - that or mod a DLP projector to get rid of the color wheel, and use custom software to split the R/G/B channels properly for the layer).
His main issue from a cost standpoint, though, has been that the cost of the photopolymer is anything but inexpensive...