I don't know about another website, but I use Fireshot for Firefox . Its features allow you to grab entire screen, or visible portion, edit, export, save in png/jpg/bmp/zip. They have a pretty good free version but if you use it a lot then you may want to get the pro for $15.
Do you prefer a web service or a locally installed application? If the latter, there's a very handy Firefox plugin (100% free) - Screengrab!. I have been using Fireshot before, but after finding Screengrab!, I have uninstalled it (Fireshot) and switched for Screengrab! for good. It works much better with very high scrollable pages.
Thanks Scorpion. I spent some time on looking for a reliable screenshot-maker, especially for the very high scrollable pages. I was disappointed with Fireshot performance - with my 4GB RAM it reported lack of memory error for pages of moderate height Another good one is FastStone Capture 5.3 - it's in fact my favourite. It's a standalone program, not a Firefox plugin. Release 5.3 was the last one available as freeware, newer versions are commercial editions. But the 5.3 was already a perfect tool, so it's really a good choice for a freebie-lovers. This free version is widely available through many free soft repositories on the web.