Thankfully, there are a handful of excellent apps - Autodesk's Sketchbook Pro foremost among them - to fill this need for Android users. Using search terms such as "sketch" and "draw" will bring up some of the most relevant products, however there is plenty of junk to wade through and some "free" or evaluation versions will install push marketing apps and may even change your browser home page so try to avoid installing anything until you've heard good things about it first (this obviously applies to more than artistic tools).
The best ones
Note: most of these apps have evaluation or free versions that you can trust.
Note on January 25, 2014: Go to this index page for all of my drawing app reviews
Note on January 13, 2014: I've realized that with the 10 or so apps I want to review, this page will get pretty long and I've had a couple of requests to change up the format and make the review longer and more in-depth so I'll break each review into its own post. I'll add "APP REVIEW:" to the title and add a keyword to them so that you'll be able to find them all easily.
Autodesk Sketchbook Pro
SketchBook Pro features drawing tools that concentrate on trying to emulate pencil, pen, marker and airbrush on paper feel, and does one of the best jobs in the industry at providing precision and accurate sampling input from a pen or stylus. The product includes basic masking tools as well as some geometric drawing tools, layers, and more.
One major feature I'd like to see added is the ability to save custom brushes.
Otherwise, for the sketcher in you, an excellent and responsive tool.
Autodesk Sketchbook Ink
You will find some slight performance hiccups now and then when the screen redraws itself, but I experienced this with other devices as well so I wouldn't see this as a Toshiba-only issue. The computations are pretty extensive to perform so zooming into a heavily cross-hatched illustration will understandably (but only occasionally) need to reset itself if there is a cache conflict. No big deal and liveable.
Drawing is a fluid process, although careful selection of brush min and max and shape will yield best results if you are using pressure to vary line thickness.
Output to higher resolutions can take some time to perform -- don't worry, it hasn't crashed, it's number-crunching your art.
If there were more functions and tools available, as well as more precise tools (such as bezier curves) I would rate it higher. We'll see if subsequent versions get feature additions.
Sketcher Pro
The drawing is extremely responsive. I would like to see more precise control somehow (perhaps with pressure or a few screen toggles), some additional tools, and the ability to make very large brushes.