I've been using licecap in various SuperĀ User answers. It's dead simple to use as you can see from this animated GIF image - just extend it over your recording area, hit record, set a save file, do your thing and hit stop. It's free, works pretty well, and seems simpler than most of the alternatives. It's entirely free and has Windows and OS X ports.
On Windows 8.1 and hdpi displays, you'll need to turn off per app display scaling to get it to work normally without turning off global display scaling. I have a walkthrough on it here (Fixed as of version 1.26.)
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Best Answer
http://www.online-image-editor.com/ Seems to do the job - I tested it roughly. Even has lolcats-text function :)