I will add some small (and rather hackish) scripts for my personal use here.
mmm (MIME multipart/alternative from Markdown) can
create a MIME multipart/alternative mail, containing a
text/plain part (in Markdown) and a text/html part, from
a Markdown file. Other mail headers (From:, To:, Subject:, ...)
can be prepended from a template file.
Usage: mmm [--file $inputfile] [--headers $templatefile]
footnotes will convert footnotes in MultiMarkDown format
to the format of the Wordpress plugin
footnotes and back.
Usage: footnotes --to mmd|wp [--file $inputfile]
pocket-raindrop will reformat a CSV export file from
Pocket into a CSV import file for
Raindrop.
Usage: pocket-raindrop part_000000.csv, output to raindrop.csv.