I just found a new feature in Excel 2010 that will save you some time. There's an optional feature at the bottom of the File>Recent menu to Quickly access this number of Recent Workbooks.
When you already have a file open in Excel, clicking the File menu will default to the Info tab so you have to click the Recent tab to see the Recent Workbook files. Checking the option mentioned above throws the Recent Workbook files (you choose how many) into the left-pane of the File menu, so you can see the files listed when clicking the File menu.
My short video shows how this new feature works in Excel 2010.