I am using the Desktop Manager application from Darwinports: it gives you virtual desktops like you get in an X-based environment. Pretty handy if you can keep your work segregated, always a struggle for me, but things seems to be movable from desktop to desktop.
So, on the topic of movable, noticed you can drag the little iconic images in the desktop panel and the application window will move. Drag Safari’s icon and see the Safari window move. I did it with Mail.app and somehow the main window became detached from the Mailboxes drawer. The drawer could now be moved independently. (See the screenshot for more).
[click for larger image]