Many have mentioned Snag-it by Techsmith, if you want strictly a screen capture tool with no editing, they also have Jing. I love it. But no editing.
Precision CAD Solutions, LLC
SpaceControl 3D Mouse - North American Reseller
A few of my colleagues use Jing, but I prefer the opensource Greenshot (http://getgreenshot.org/). I've used it in XP and 7, and it is configurable to allow annotating or not. You can set different hotkeys for the type of capture you are wanting (area, window, screen) and the destination (clipboard, file, editor, printer, email, or any combination). I've used it ever since my company disallowed the use of Gadwin Printscreen (since its freeware version is only for personal use).