This version of procmail supports Maildir folders.

To make procmail to deliver into a Maildir folder, just append
a slash (/) to the name of the maildir folder in your ~/.procmailrc file.
For example, the following rule:

:0
* ^List-Id: [^<]*<community\.lists\.altlinux\.org>
community/

will deliver all mail from the ALT Linux general discussion mailing list
to the Maildir folder "community".