i haven't set up clamav to run as a milter on my servers - yet. yes, i know about mailscanner, amavis and friends...they're all too fat for what i want, and clamav's mail parsing facilities (at least in the versions i could get onto my Debian/stable servers) are nonexistant. so i've got dual queues, between which some kind of filter is moving stuff after scanning.
my small script is a simple wrapper around MIME::Parser (see libmime-perl in debian) that reads sendmail queue files, extracts the content into a tempdir, runs clamscan on that and depending on the result, moves the stuff into the quarantine or the real mail queue. Feel free to (ab|re|per)use.