Updates to OpenBSD's IPSec support back in 2007. very kick ass.
This is a nice easy reference for 2 OpenBSD peers creating an IPSec VPN:
And the short version of the above:
This one doesn't really have anything to do with IPSec but I thought it was funny:
And here is a list of papers related to OpenBSD:
If you are a startup, or IT department on a tight budget and need a new VPN solution for next to nothing(grab an old 1U P3/P4 supermicro) Check out this page for setting up OpenVPN on OpenBSD:
We use all of the above technologies at my work and they are amazing pieces of FOSS. I support the OpenBSD team as much as possible and buy the CDs, T-shirts, mugs, etc...and am hoping to get work to donate some money for the thousands we've saved by using OpenBSD instead of a cookie cutter, expensive VPN solution.