I have a formula in an excel spreadsheet linked to a spreadsheet in another workbook... now I can't remember where I saved that other workbook, is there a way to find it?

Look in the cell with the references, it should show the complete path to the file:

='C:\Documents and Settings\Jerry\My Documents\Excel Tips\[AAG Log.xls]Sheet1'!$A$1


Another way to find it is to click on Edit > Links, click on Source filename and click on Open Source.