Comparison of different flavors of Markdown

[Harold Tessmann III]

At the risk of starting another shi^W reasonable discussion between
mature adults, is there a site or page that compares, or even lists,
the various flavors of Markdown? I've found comparisons of Markdown
with other languages, and references on different Markdown plug-ins
for other environments (Wordpress, etc.), but not a simple list of
what different versions of the script people have made public. (And
yes, I will most likely customize whichever version I choose to add
more specific features that I want. That wouldn't be the most
questionably necessary development I've done on this project.)

Harold