Lifehacker has consistently been one of the most useful websites for me in and out of the classroom since I first started reading it. It's a blog focused on productivity and efficiency--two keys for a long, successful career in education. You should certainly be reading their site regularly already, but for those who haven't subscribed yet, here's five recent examples of great new resources:
Calculate Your Activity-Specific Calorie Burn with Wolfram Alpha
NumberQuotes Gives Perspective to Your Statistics, Is Great for Presentations
Export All Your Google Docs to a ZIP File - You should always be backing up your work!
Embed PDFs and PowerPoint Files for No-Software Viewing - For your class blog or one you use for sharing resources with your colleagues.
Break Your Cycle of Stress with Guilt-Free Vacations - If you don't feel like you need this already, you will... soon.