Update 8/2012: Recently the Snipping Tool Website disappeared from the web. I have provided a replacement download location for the tool on one of my servers see the link at the bottom of this article. Sorry I do not have screen shots currently.
The Snipping Tool first introduced in Windows XP Tablet edition experience pack and now part of Windows Vista and Windows 7 is a useful tool to capture and copy a portion of your computer screen to paste into blogs and documents.
(note: To install snipping tool in Windows Vista go to the Control panel choose Programs and features, Click on Turn Windows Features on or off, check the box next to Tablet PC Optional Components in the popup. Click OK, once installed snipping tool will show up in your accesories folder.) The snipping tool is preinstalled and under Accessories folder in Windows 7 start menu.
It is a basic replacement for the Printscreen method of copying and pasting a screen which is not as granular and gives you a larger item when you paste it. I've seen lots of questions about how to get this functionality under the regular XP version. Snippy is the answer.
The free tool Snippy puts an icon of a pair of scissors in your task tray and when clicked on gives you a pencil cursor that you can use your mouse to trace around the area you want to clip and copy with a mouse click so you can paste it into any type of document. There is no installation required for Snippy, you just save the file and click on it to run. You can even just save it to your desktop so you can have it handy.
You can download Snippy from here. Note that it is an exe file and your browser may warn you about it. The file is safe and OK to download. You can save it directly to your desktop and run snippy.exe right from there.