Simple Online Drawing Tool
This is a relatively straightfoward contender in the online drawing world. It looks like the site has been around since 2007. The creator says "my hope is to create a powerful and easy to use web drawing tool that you can use to create and edit images, and use them all over the internet." No login is required. Rudimentary layers, a selection of stamps and shapes, fonts and sizes, and the ability to upload images or point to a URL are all welcome features.
While still in "beta" (for almost 5 years), it is an easy tool to use, and artists can easily download, email or embed their creations.
(See Tammy Worcester's Tip of the Week for more details.)