The YubiKey NEO

I put together a HOWTO several months ago for configuring the YubiKey NEO as an OpenPGP/GnuPG smartcard token, including OpenSSH key manager integration:

http://25thandclement.com/~william/YubiKey_NEO.html

I mostly use it to authenticate SSH sessions (using public-private keys, not the HOTP feature) and sign Git logs. Very nice product. I also hava a bunch of regular YubiKeys which just do HOTP, but you have to use one per server unless you setup a centralized auth server (or if your bold enough to use an commercial authentication service).