Got three Dell 2001FP displays side-by side.  The leftmost one has the video editor running on it (Premiere or Avid), the middle one has whatever else I'm working on displayed on it (graphics, HTML, documents), and the rightmost one has command palettes for the application on the middle display and either a browser (if I'm writing HTML) or thumbnails of the source materials I'm working with.
When I do development, the left one gets the documentation and release notes that I'm writing or the debugging info, the middle one has the source editor, and the rightmost one runs the software.