The above option pricing spreadsheet will allow you to price European call and put options. You can also enter up to ten different option/stock leg combinations to view the expected payoff at expiration.
If you have trouble with the formulas, check out the support page.
Alternatively, you can visit the online version of these calculations at Option-Price.com
Just to note that much of what I have learnt that made this spreadsheet possible was taken from the highly acclaimed book on financial modeling by Simon Benninga - Financial Modeling - 3rd Edition
If you're an Excel junkie, you'll love this book - Simon's a freak. There are loads of real world problems that Simon solves using Excel. The book also comes with a disk that contains all the exercises Simon illustrates. You can find a copy of Financial Modeling at Amazon of course.