Awesome Screenshot is light-weight, straightforward, and very useful. You use it to take a screenshot of a site’s entire page, or just what you see in your browser window. And you can draw on your screenshot, add notes, crop it down, save it, share it, and more.
Although it doesn’t have some of the extra functionality and personality of Coda Notes, Awesome Screenshot seems snappier and more reliable (I’ve sent several Coda Notes that never made it to the recipients, though it may have been operator error because you have to type in recipient emails by hand.). And so this is one reason I like Awesome Screenshot — you can save your annotated screenshot to your computer and then email it using your own email client.