ScreenGrab is one of my favorite Firefox extensions that I use very frequently. One of the best features in ScreenGrab is the ability to take screenshot of a specific region of a webpage. This is great if you want to a quick screenshot for your blog. I use it even to copy part of images directly from the browser without having to open Photoshop to cut or resize. Notice that ScreenGrab support saving screenshot in JPEG format, which is better if your screenshots include photos, otherwise PNG is perfect for most other cases.