Remote access tunnel

[Chris71Mach1]

I'm working with a Nortel Contivity 100s that's running 1.2-BETA-1-TESTING-SNAPSHOT-06-06-2007 firmware, and I am looking to set up a remote access VPN so I can connect to my network when mobile (akin to mobile employees using a client to tunnel into their employer's network).  I was wondering if anybody knew of a good howto on how to accomplish this, as well as a recommendation for a good client for both Windows and Linux.

Thanks!