View Source Choice
[r]edirect View Source to current window (current default in Firefox), new tab, or new window.
Thanks Brian — I've installed the extension, and it works great! The planned ability to override the view source keyboard shortcut already has me anticipating version 0.2.
Update 2006-01-20: View Source Choice has been updated and now features an optional override.
This functionality is already in the Web Developer extension if you choose preferences when viewing your extensions! :-)
Does the extension also add the view-source UI to the window it's showing the source in?