Since Excel likes to open all the spreadsheets into one window it makes it difficult to use both of your monitors. To work around this I realized that you can simply right click on the task bar icon for excel and click on the Excel icon towards the bottom to open another instance of excel which you can then move where ever you would like.
Not sure why it took me so long to figure out I could do this since I use this technique all the time for IE and Firefox.
