Trillian

Trillian is a sophisticated, powerful tool for communicating with your contacts via IM.

The program is also capable of working with all of your MSN, Yahoo Messenger, AOL Instant Messenger (AIM), ICQ, and IRC accounts simultaneously.

Trillian is fully compatible with all of these servers, has its own environment (very comfortable and easy-to-use), and can be customized with different skins.

The program also supports log-in and log-out registries, lets you use emoticons, and has its own icon system for differentiating between each of your online contacts.

If you have several accounts on different servers, this is the application you've been looking for.