We find these books incredibly useful.
- Persuasive Online Copywriting - How to Take Your Words to the bank, Bryan Eisenberg, Jeffrey Eisenberg, Lisa Davis.
- Don't Make Me Think - Steve Krug
- Web Standards Solutions - The Markup and Style Handbook, Dan Cederholm
- Pro Drupal Development, John K VanDyk and Matt Westgate
- Pro Javascript Techniques, John Resig
- PHP 5 Objects, Patterns and Practice, Matt Zandstra
- The principles of beautiful web design, Jason Beard
- The Long Tail, Chris Anderson
- The Tipping Point, Malcolm Gladwell