I have a collection of Excel books that have helped me out tremendously.
I love the Excel books by John Walkenbach. He's got one on formulas, VBA, and Charts respectively.
I've got Mr. Excel's VBA and Macros for Microsoft Excel... very helpful book.
Just yesterday, I've purchased the Dashboard Reporting Toolkit advertised at the top of this site. I fell in love with it right away and will soon try to design a few of these reports for my work. They will definitely "make spreadsheets look good"!
As for websites, this is my #1 site to come for help. The good way to get other good websites is to look through the "Helpful Links" section of any good web site that you come across.