[Kombisaurus]

http://www.skitch.com/

It's a very quick and simple screen-grab and annotation utility. Ideal for me as a developer where I often need to take screenshots and send emails with instructions attached. Also perfect for posting step-by-step instructions to blogs/forums and so on. It doesn't do anything that can't already be done, just eliminates all the steps and hassle.

Let us know how you get on, and I'll let you know my first impressions.