"FireShot is a Firefox extension that creates screenshots of web pages. Unlike other extensions, this plugin provides a set of editing and annotation tools, which let users quickly modify captures and insert text and graphical annotations. Such functionality will be especially useful for web designers, testers and content reviewers. It's possible to choose whether entire web page or only visible part of this page should be captured. Screenshots can be uploaded to server, saved to disk (PNG, GIF, JPEG, BMP), copied to clipboard, e-mailed and sent to external editor for further processing."
So yeah, I downloaded this Fireshot dealie a couple of days ago and it's great for capturing exactly what you want on a website; even catches flash images and stuff that printscreen can miss. I'm not trying to design a website at the moment but I will be this summer so this baby'll do wonders when I'm breaking down sites and such.