Visual Studio 2010 will have better support for a multi-monitor setup, but it's possible to get part of the way in 2008 already.
Toolbars and property windows (e.g. Solution Explorer, Class View) can be dragged into separate windows (2010 will add the ability to drag documents into separate windows too):
Window positioning gets a bit weird when you switch from one monitor to another, or change resolutions - a common occurrence when you're a laptop user docking and un-docking.
You can create two settings files, one for your single monitor layout, and one for your multi-monitor layout, and use them when starting Visual Studio 2008:
Now you have two or more settings files, you just need to create a shortcut icon for each one somewhere in your start menu.
Edit the target, and add the parameter /resetsettings D:\multimon.vssettings to the end (replace the path with each settings file path).
Now when you launch your new shortcut, it will start Visual Studio 2008 with the correct window layout. Because you only exported and imported the Window Layouts, all the other settings stay the same.
You may also want to make these changes to your shortcut:
Cheers,
Kirk
Previous VS2008 Tips:
Disclaimer The opinions expressed herein are my own personal opinions and do not represent my employer's view in any way.