Here are the best articles I’ve read about Heartbleed – what it is and why it’s scary.
From TidBITS: The Normal Person’s Guide to the Heartbleed Vulnerability
From Mashable: The Heartbleed Hit List: The Passwords You Need to Change Right Now
From The Unofficial Apple Weblog: Manage Your Passwords and Protect Yourself from Heartbleed
From Small Dog: Heartbroken About Heartbleed? Don’t Be! Here’s What You Need to Know