Mail Perspectives v1.1.2

Your email is often something you want close at hand but never in the way. Whether you want to see the latest message or the recent message list, Mail Perspective's compact window design means your email can always be visually available, but never the focus of your attention until you need it.
Monitor Important Mailboxes
Sure your inbox is important -- but if you are like many Mail users, you probably have several Mailboxes which are just as important if not more so. Use Mail Perspectives to create a compact Perspective window for each of your critical mailboxes. Use the All/New/Today bar to tailor which messages they will show.

Tame Mail Window Chaos
Navigating Mail's windows can be a handful when you want to open different viewers, mailboxes to find messages. With Mail Perspectives you can save your preferred window arrangement and restore it at any time with a mouse click or keystroke. It's like coming home to tranquility after a busy afternoon of running errands.

Homepage: http://indev.ca/MailPerspectives.html

Mac OS X 10.6+ and Mail.app