
If you have the need to create MS VPN tunnels from your Linux box, then this link may be interesting to you;
http://www.ghacks.net/2010/03/02/connecting-to-a-microsoft-vpn-with-linux/
I got a newsletter some time ago informing me that www.Yubico.com (or rather one of it’s partners) had added AD integration to the Yubikey, this should allow you to use the Yubikey to login to windows something that could be quite interesting..
Read more here;
http://www.yubico.com/news/100204/
ps.
I also seem to recall stumbling across some PAM and RADIUS implementation, so you might want to check their forum if you are into Yubikeys.
http://forum.yubico.com/