I'll vouch for the Yubikey HOTP system: www.yubico.com. Yubikeys are quite slick. They're much faster than even typing in a short TOTP string, yet still don't require any client software. They pose as a USB keyboard. When you press the button the next OTP is printed along with a line feed. Works for SSH, HTML web forms, etc.
When I create a new shell account on my server I hand one of these out.
I just bought 10 for $99 (holiday special). I think if these were in the $3-$5 range they'd sell much better, but what do I know.
Yubico also sells a tiny USB hardware security module to securely (i.e. irretrievably) store the OTP secrets for authentication. It's pricey but still the cheapest HSM solution by far that I'm aware of. The HSM isn't necessary, of course, but it's an extremely nice option.