Here are a bunch of articles and other references that you may want to check up on once in a while. I add more all the time.

• Arduino Hacks
• All About Batteries
• Electrical Engineering Tools
• Where to Find Parts
• How to Design and Sell Kits
• Laser Engraver/Cutter Ideas and Techniques
• Microcontroller Annoyances
• Open Source Hardware
• PCB Design & Fabrication
• PIC vs. AVR Smackdown