Atricore’s JOSSO is an open source and commercially supported Internet Single Sign-On (FSSO) solution for point-and-click and standards-based (SAML2) Internet-scale SSO implementations. For more information contact us at : http://www.josso.org
...It is a flexible, extensible, and secure alternative to tokens, certs and passwords. Application & API support exists for Java, ASP, PHP, Ruby, OpenVPN, TACACS+, etc.
Read our eGuide on how to setup your network with two-factor authentication: http://www.wikidsystems.com/learn-more/two-factor-authentication-white-papers