Here are some links to help understand and react to the Heartbleed bug.
What is Heartbleed?
Here is a site that has been regularly updated with information about the Heartbleed bug. http://heartbleed.com/
Here is a list of poplular websites and a status on whether they are vulnerable. http://www.cnet.com/how-to/which-sites-have-patched-the-heartbleed-bug/
If the site you’re interested in was not on the list above, here are two pages you can use to check if a website is still vulnerable to the Heartbleed bug. https://filippo.io/Heartbleed/ https://lastpass.com/heartbleed/
How does it work?
Here is a great webcomic by xkcd that simply explains how the Heartbleed bug is exploited. https://xkcd.com/1354/
What Can I Do?
Here is a link where you can get a plugin for your Firefox and Chorme browsers, to detect websites vulnerable to Heartbleed, before you log in. https://www.techsupportalert.com/content/firefox-and-chrome-browser-extensions-check-heartbleed.htm
If you’re more technical, check out the following video for more details about the bug. http://vimeo.com/91425662