Following up to my own post so that this gets in to the archives and 
hopefully helps someone else.

Nik Clayton wrote:
> Has anyone managed to get a FreeBSD PPTP *client* to talk to a m0n0wall 
> PPTP *server*?
> 
> I've set up the aforementioned PPTP server in m0n0wall and it works.  I 
> know that it works because I have both Windows and Mac OS X clients 
> using it and it works for them with no problems.
> 
> I had expected it to be similarly easy to get it to work on FreeBSD.  
> I'm using the pptpclient port (ports/net/pptpclient).

It wasn't.  I couldn't get pptpclient to work.  So I switched to 'mpd' 
(ports/net/mpd).  If anyone else is doing this, the following should help.

In $PREFIX/etc/mpd.links put these lines:

   vpnlink:
           set link type pptp
           set pptp peer 192.168.2.1
           set pptp enable originate outcall


Adjust the 'set pptp peer' line to whichever IP address you have m0n0wall's 
PPTP server listening on.

In $PREFIX/etc/mpd.conf put these lines:

   vpn:
           new vpn vpnlink
           set bundle disable multilink
           set bundle authname AUTHNAME
           set bundle password PASSWORD
           set iface route default
           set link mtu 1460
           set link no pap afcomp protocomp
           set link disable chap
           set link accept chap
           set link keep-alive 60 180
           set ipcp no vjcomp
           set bundle enable compression
           set ccp yes mppc
           set ccp yes mpp-e40
           set ccp yes mpp-e128
           set ccp yes mpp-stateless
           set bundle enable crypt-reqd
           open

Adjust AUTHNAME and PASSWORD to match whatever PPTP username and password 
you've configured in m0n0wall.

You should now be able to:

     # mpd vpn

and watch as it establishes the PPTP connection for you.

Proof that this works is this e-mail message, which is going over a wireless 
pptp connection to my m0n0wall server...

N