summing (or other calculation) on specific cells through multiple worksheets.
for example, if you have 50 worksheets, from "FirstSheet, SecondSheet, ThirdSheet…LastSheet" you can sum every instance of cell G6 with this simple formula:
you can even add mew worksheets between FirstSheet and LastSheet.
This is awesome for multiple business cases or product line financials or whatever.
(thank you to http://www.officearticles.com/excel/sum_the_same_cell_in_multiple_microsoft_excel_worksheets.htm for teaching me this)