> Hello. What open source and free(dom) reverbs do we have available?
There are GVerb, Freeverb, TAP Reverberator AFAIK.
TAP Reverberator is also a standalone program where you can edit much
more as in the ladspa plugin, then you can load this as a preset in ladspa.
> What free (possibly not open source) reverbs do you use?
There are also some free VST reverbs which I tried with ardour on linux:
Ambience, Transverb, Classic Reverb
For more see here: http://ardour.org/node/1079
> What kind of reverb presets people use for vocals?
Try them and then decide for yourself ... ;)