Google Talk
The connection between the Google Talk client and the Google Talk server is encrypted, except when using Gmail's chat over HTTP, a federated network that doesn't support encryption, or when using a proxy like IMLogic. End-to-end messages are unencrypted. Google plans to add support for chat and call encryption in a future release. Some XMPP clients natively support encryption with Google Talk's servers. It is possible to have end-to-end encryption over the Google Talk network using OTR (off-the-record) encryption using other chat clients like Adium (for Mac) or Pidgin (for Linux and Windows).