A comprehensive list of Metafont fonts used to be posted to comp.fonts and to comp.text.tex, roughly every six weeks, by Lee Quin.
Nowadays, authors of new material in Metafont are few and far between (and mostly designing highly specialised things with limited appeal to ordinary users). Most new fonts that appear are prepared in some scalable outline form or other (see "choice of scalable fonts"), and they are almost all distributed under commercial terms.
This question on the Web: http://www.tex.ac.uk/cgi-bin/texfaq2html?label=findfont