HTML5 online painting app Muro is a surprisingly capable drawing app that doesn't require Flash, plug-ins or anything else — just a browser that supports the latest technologies.
The application works well in any HTML5-compatible browser, which is basically all of them except for Internet Explorer — though it's obviously a lot easier to use if you've got a drawing tablet as well. The application also works surprisingly well on your iPad — the touchscreen is an ideal platform for a drawing application. There's a good set of drawing tools and a whole slew of filters for blurring, sharpening, embossing or any other image editing type of task once you're done with your image. It's a great tool worth a look, if for no other reason than to see what HTML5 is capable of.