IPSec notes...

Updates to OpenBSD's IPSec support back in 2007. very kick ass.

http://www.openbsd.org/papers/asiabsdcon07-ipsec/index.html

This is a nice easy reference for 2 OpenBSD peers creating an IPSec VPN:

http://www.packetmischief.ca/openbsd/doc/ipsec.html

And the short version of the above:

http://m4dsk1llz.wordpress.com/2008/08/14/site-to-site-ipsec-vpn-using-openbsd/

This one doesn't really have anything to do with IPSec but I thought it was funny:

http://www.openbsd.org/papers/f2k9-vrf/index.html

And here is a list of papers related to OpenBSD:
http://www.openbsd.org/papers/

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:

http://www.kernel-panic.it/openbsd/vpn/vpn4.html

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.