When I posted the original question, I though Excel was used for adding up columns. Then, some of the responses got more and more complex. Today, I found out what all this knowledge is actually used for:

From the New York Post:

Banker rates dates in a spreadsheet -- then shares the file with one of them

and some commentary:

Real men can close the deal without opening Excel

Seriously, thank you for all the advice. Any suggestions of more online and DVD courses will be appreciated.