Mac OS X: Sometimes you end up with an image in your clipboard that you'd like to save to a file. There are a few ways you can do this, but one of the fastest and easiest methods is using Mac OS X's built-in app Preview.
All you have to do is copy an image, open up Preview, and choose "New Image from Clipboard" in the File menu. The image in your clipboard will then show up like any image you've opened in Preview, giving you all the options you have with standard image files. You can edit it as you like, then save it out to one of many format options, or email it. This is a really fast and easy way to save out images stuck in your clipboard.
Getting a graphic on the clipboard to disk? [StackExchange]