Hometracked has a nice collection of links for all you handy DIY musicians interested in building your own reverb unit.
From the article:
A custom reverb can add a unique signature to your recordings. And since practically every space reverberates, a home made reverb often requires no more than a speaker, and microphone to capture reflected sound. Understandably, then, reverb units are popular do-it-yourself projects for musicians and recording engineers.
If you’re not the DIY-type (I already have to resign if it involves any soldering…) you can always use a impulse response plugin like SIR and use someone else’s signature reverbs.