This add-on adds a small screenshot capture button to the top right of your browser. There are several options for capture, including uploading the visible area of the browser only or uploading the entire web page. Screenshots are uploaded to the free screenshot hosting website UploadScreenshot.com.
A quick demo video can be viewed at: http://www.youtube.com/watch?v=OaZk_mwGNvc
"Screenshots" are often also referred to as a: screen grab, screen capture, print screen, etc. The add-on is free to use, and the UploadScreenshot.com site is advertisement free.
See here: http://www.uploadscreenshot.com/ff-tutorial
Optional, Free, User Accounts
User accounts allow you to describe, delete, view, and search through the text contents of your screenshots. For screenshots taken with the addon a link back to where the screenshot was taken is shown in your private account.
Screenshots taken while logged in to the site will automatically be added to your account. If you are not logged in when you upload a screenshot you will be given one chance to login right after the upload to claim the screenshot, adding it to your account.
Sign up page: http://www.uploadscreenshot.com/signup