Nowadays, new fonts are seldom developed by industrious people using MetaFont, but if such do appear, they will nowadays be distributed in the same way as any other part of (La)TeX collections. (An historical review of Metafont fonts available is held on CTAN as “MetaFont font list”.)
Nowadays, most new fonts that appear are only available in some scalable outline form, and a large proportion is distributed under commercial terms. Such fonts will only make their way to the free distributions (at least TeX Live and MiKTeX) if their licensing is such that the distributions can accept them. Commercial fonts (those you have to pay for) do not get to distributions, though support for some of them is held by CTAN.
Arranging for a new font to be usable by (La)TeX is very different, depending on which type of font it is, and which TeX-alike engine you are using; roughly speaking:
dvips, and pdfTeX are “happy” with them. While a new font will need “generating” (by running MetaFont, etc.), distributions are set up to do that “on the fly” and to save the results (for next time).
vffiles have been created from their metric (
mapfiles also need to be created. Such fonts will work with pdfTeX, and with the (“vanilla”)(La)TeX and
The answer “choice of scalable fonts” discusses fonts that are configured for general (both textual and mathematical) use with (La)TeX. The list of such fonts is sufficiently short that they can all be discussed in one answer.