auth2x is a Perl module for performing 2-factor authentication. auth2x has a user authenticate with a passphrase initially. If that authenticates, the module sends a 10 character hex code to a pre-configured (per authentication user-basis) email address. The user then authenticates a second time with their passphrase concatenated with the 10 character code.
The HOTP Toolkit package contains tools that are useful when deploying the one-time password HOTP technology. It contains a shared library, a command-line tool to generate and validate one-time passwords, and a PAM module (pam_hotp) to make system login or SSH use HOTP one-time passwords for authentication.
sec-wall is a feature-packed security proxy that supports SSL/TLS, WS-Security, HTTP Auth Basic/Digest, extensible authentication schemes based on custom HTTP headers and XPath expressions, powerful URL matching/rewriting, and an optional header enrichment. It's a security wall with which you can conveniently fence otherwise defenseless backend servers.
dynalogin is a distributed two-factor authentication suite that combines a secure UNIX server and API with an Android soft token. Open standards (HOTP, TOTP, and soon OCRA) are used for one-time passwords. A C library is provided for inclusion in existing software and Web sites. OpenID (using SimpleID) is supported for Web applications and single sign on. PAM is supported for easy UNIX and LDAP integration (SASL, RADIUS, and JAAS in development). It works with Google Authenticator or the dynalogin Android application.