So this idea just popped into my head so I decided to sketch up a little diagram. There's plenty of DIY reverbs made with slinkys but in my opinion [though they sound pretty good] they're not practical. It would be a real pain in the ass to have to tear it down every time you needed to move it, especially if you were in a gigging band or something. You could always box it up, but slinky's a freakin' long.
So what's my idea? Well have you ever put a piece of PVC tubing up to your mouth and used it like a digeredoo? It's fairly reverby, eh? why not put a an amplifier and speaker on one end, and another amplifier and mic on the other?
Now I haven't built this yet, and it'll probably be a while until I do, so I don't know if it works, but in my head it should work as a fairly decent mini reverb chamber.
Anyway, take a look at my crappy sketch, and if you have any ideas, or if you have built it, let me know.