Skitch was an application I really didn’t understand at first – why would you need anything more than the built in OS X screenshot utility? Boy, was I wrong.
Skitch combines a very flexible screenshot tool with good annotation and drawing tools, plus one click posting to the web. It fully supports tablets for drawing on your screenshots, and gives you simple ways to get your images out of Skitch and into an email, instant message, etc.
So, if you’re an OS X user that occasionally needs to send people screengrabs to explain something, it’s definitely worth a look. You can follow my skitch feed here, or just download Skitch for free and give it a try.