AudioGeeks, rejoice: MVerb an astounding little reverb plugin, pro quality sound, fairly extensive controls, low processor draw and did I mention it's free? And open source? GarageBand, Live, Logic, Mac, Windows, it seems to work everywhere.
Obligatory public service announcement: with any reverb, you should always try to set the mix ration of dry/wet signal to 70/30, and tweak from there. On this little wonder, start at a setting of around 0.25 for the Mix knob, and adjust down, to less reverb. It's like salt - a little goes a long way. Reverb is an easy way to add a little virtual "air", or space, around any sound, but especially those generated artificially, like drum machines and synthesizers, as well as close-captured vocals. This thing sounds really, really good, it's a gem of a tool.