We here at SparkLabs are big fans of pfSense, using it to manage both our work and home networks. We also know a great number of Viscosity users connect to routers running pfSense, so we were very happy to see Viscosity featured in pfSense: The Definitive Guide by Christopher M. Buechler and Jim Pingle.
"If you use OpenVPN frequently, Viscosity is a much nicer client and well worth the cost."
As well as covering a great deal about network setup, the book also contains an in depth section dedicated to setting up pfSense to act as an OpenVPN server. It contains a great deal of information about how to configure and use Viscosity to connect to your pfSense router.
We highly recommend picking up a copy of pfSense: The Definitive Guide if you are interested in setting up your own pfSense OpenVPN server and using Viscosity to connect to it.
Check out the website for more information.