I don't know if others are using "vi" as well but I recently added a
command to vim to run Markdown on chosen bits of text for me.
I edited ~/.vimrc and added this line:
:com -range=% -nargs=* FilterText <line1>,<line2>!SmartyPants.pl | Markdown.pl
It filters the chosen text through both SmartyPants and Markdown and
all I have to do is ":F" (after a visual select) or for the whole
document ":1,$F", etc (like any other "vi" command).
Hope this is useful to some and not "in the way" for others :)
-- Sarah