An easy route would be to dump it to a comma separated text file - in other words, your microcontroller would print (without line feeds) a value, a comma, a value, a comma, etc, then println(",") to end that row with a comma.
The computer end - You can send that to hyperterminal and write the results to a .txt file, rename it to .csv and import it directly into excel. If you want it to be automated, take a look at Visual Basic 2010 - You should be able to piece together some sample code to write the serial directly to a .csv. You can open them with excel, but you have to open excel first, then open the file from within excel, and it will launch a wizard to import your data.