From The Proteus Community:
Multi-service instant message application.
- Out of the box support for AIM (including .Mac accounts), MSN, Yahoo, ICQ, Jabber, iChat Rendezvous, Gadu Gadu, and Sametime messaging services.
- Drag and drop addition of new services via 'Service Plug-ins'.
- Allows multiple accounts on the same services at the same time.
- Supports custom away messages, so you can tell people exactly why you're ignoring them.
- Have a single-window for all your incoming messages, or just some of them.
- Integrates with Apple's Address Book on a per contact basis.
- Includes a Dock Menu and a System Menu Item, allowing one-click access to the most common controls.
- Includes gorgeus Aqua eye candy like animations window transparency.
- An icon you won't mind having in your dock.
- Utilizes Apple's text-to-speech engine, giving your messages a voice.
- Execute shell commands for incoming messages.
- Customize your emoticons, your sounds, your colors, your fonts, and your status images.
- Share your favorite customizations with your friends through Proteus Packs.
- Proteus is currently localized in English, French, German and Traditional Chinese, with more coming.