AMT Turbines make small turbines, I've seen a single seater homebuilt with two of their turbines strapped up front, cannot find a pic of it on the Net, but it's been done.
I've also met guys who put APU's into an airframe but it's not ideal as APU's were not designed for this job.
If you want to do it yourself,
ft is on the right track, head down to your local scrap yard and pull a turbocharger. Just keep away from my gaff, not that you will ever get the beast off the ground, you might just burn my house down
Best thing to put in a homebuilt right now is a used Lycoming IMO, but then I'm a puss. Where I live it's important to know your motor isn't going to go tits up, it interferes with my snoozing having to keep an eye out for emergency landing sites.
[ 14 November 2001: Message edited by: slim_slag ]