Pixlr to someone who needed a quick way to resize and change the colors of an image. Pixlr offers a large set of image creation and editing tools. One of the tools that can be quite handy is Pixlr Grabber. Pixlr Grabber is Pixlr's screen capture tool. Pixlr Grabber is available as an extension for Chrome or Firefox. Using Pixlr Grabber you can capture your screen, crop the screen image, and print what you like. You can also send the image to Pixlr Editor for further editing options.
Applications for Education
I always find it helps to have screen captures ready to send, post, or print for students to reference when I'm introducing them to new tools. I don't think that Pixlr Grabber offers anything that makes it significantly better than any other screen capture tool. That said, if you're looking for a screen capture tool to add to your browser, Pixlr Grabber will get the job done.