Meebo is an all-star instant messaging software that allows you to sign in to your IM accounts all at once. The firefox plugin allows you to keep tabs on all your contacts directly through through the browser, no need to have all those programs open in your system tray sucking memory.

Meebo also plays nicely with your blog, allowing you to embed a meebome widget for IM and chat directly into your pages.

Nice, clean interface too. Check out Meebo.com