the following are the perl programs i use to integrate pgp with mail
and tin (my newsreader of choice). they seem to work pretty well, but
they are hacks first & foremost, so you'll have to tweak them to get
them to work on your system. if you come up with any improvements
i'd appreciate a copy. other than that, do with 'em what you will.

these are the programs:
   morepgp: a pipe and wrapper for more (or your standard pager) which
            extracts PGP blocks and runs them through PGP.
   mailpgp: a wrapper for vi (or your standard visual editor) which
            gives the user the option of signing & encrypting a message
            when they finish editing it.
   postpgp: another vi wrapper, which only gives the option of signing
            a message & handles environment variables slightly differently
            since tin doesn't have a set of its own.

installing with mail:
   in your .mailrc, set the mail PAGER variable to morepgp, and the
   VISUAL variable to mailpgp. make sure both programs are in your
   path (or their paths are fully specified in the vars) and that the
   #! lines correctly point to perl on your system.

installing with tin (may apply to other newsreaders too, but no guarantees):
   write a shell wrapper for your newsreader that sets the variable
   VISUALBAK from $VISUAL and sets VISUAL to postpgp before calling
   the newsreader. the newsreader will then call postpgp whenever you
   edit a new post, allowing you the opportunity to sign the message
   before sending it.

bugs:
   mailpgp & postpgp only sign/encrypt the -last- item on the
   command line. this isn't normally a problem since i never edit
   more than one file for news or mail. if it is for you, change 'em
   & send me updates.