Yahoo Messenger Allows you to instant message with anyone on the Yahoo server. Tells you when you get mail, and gives stock quotes. http://messenger.yahoo.com/

Y!TunnelPro Add-on aiming to protect Messenger users from abusive and malicious chatroom activity. [Requires Windows]. http://www.ytunnelpro.com/

BuddySpace A Java implementation of Jabber instant messaging. It adds maps and semantic web services to a cross-platform messaging tool that interoperates with ICQ, MSN, Yahoo, and AIM. http://kmi.open.ac.uk/projects/buddyspace/