Meebo is an online Instant messenger that let's you communicated with Yahoo Messenger, MSN, Googletalk, ICQ and AIM users. Sign up and it will log you into to all your accounts without having to have downloaded the clients for either service. The log in page can also pop out to look like a standalone application. A great way to access all those IM services and to have access to most Instant messaging on any computer without needing to download anything.