Off-the-Record (OTR) Messaging is a gaim plugin which allows you to have private conversations over the instant messaging system of your choice. It provides encryption, which prevents someone who intercepts your instant messages from reading them; authentication, which ensures that the correspondent is who you think it is; and perfect forward secrecy, which ensures that no previous conversation is compromised if you lose control of your private keys.
The Off-the-Record (OTR) Messaging proxy is a multi- platform proxy that allows you to have private conversations using the AIM client of your choice. It provides encryption, which prevents someone who intercepts your instant messages from reading them, authentication, which ensures that the correspondent is who you think it is, and perfect forward secrecy, which ensures that no previous conversation is compromised if you lose control of your private keys.
WebSecure4Linux is a simple, unofficial Linux client for the Freedom WebSecure service (see http://www.freedom.net/products/websecure/). Zero-Knowledge Systems runs the service and provides a Windows client, but is not responsible for this Linux client. Note that you will need to sign up for the service before this client will operate. It currently supports HTTP on all versions of Linux, and HTTPS is supported under Linux 2.4. WebSecure4Linux is not feature-complete and it is slow. It's written in Perl, and forks for each Web connection.