The web is loaded with great Excel resources, but below are a few of my favorites.  Let me know if you think I’m missing any.

Mr Excel — amazing discussion board and lots of books and videos on Excel (owned by Bill Jelen)

Chandoo — incredible blog, plus some Excel courses and templates, and an active discussion board (run by Purna Duggirala, aka Chandoo)

The Spreadsheet Page — Excel discussion board, plus great tips, downloads and books (run by prolific author John Walkenbach)

Excel Forum — big Excel discussion board

Contextures — Excel tips and tutorials, along with a blog (run by Debra Dalgleish)

Excel Jet — lots of tips, a blog and video courses (run by Dave and Lisa Bruns)

Peltier Tech — advanced charting and VBA stuff (run by Jon Peltier)

Excel Tips — just what it says (run by Alan Wyatt)

Excel TV — Excel tutorials and interviews for true Excel geeks (run by Rick Grantham)

Daily Dose Of Excel — a good blog (with multiple contributors) another site for mutant Excel nerds

Microsoft — free Excel video tutorials for Excel 2010, especially good for beginners (you can find similar links for the other versions of Excel)