Meebo.com

Meebo is a website that allows AIM, MSN Messenger, Yahoo! Messenger, ICQ, GoogleTalk, or Jabber users to use their services to chat.

The user does not have to load any software on their machine, and the service can be accessed from anywhere on the internet. Recently, Meebo added the ability to create Meebo accounts, which allow advanced functionality like automatic sign-in to multiple accounts and chat log tracking.