Sorry I missed a post last week. I was with my mom, post cataract surgery, all went well, but internet service at her house is dependent of the wind blowing the right way and a neighbor who doesn't have his web access password protected! But, to make up for it, I'm putting one of my favorite apps on display: Paper by 53.
Paper is a popular, and comparatively expensive app -- I think for all the tools, you'll pay $7.99. But, think of that as an endless set of sketchpads and unlimited inks, pencils, markers and watercolors.
The tools are elegant, and the interface intuitive. You'll also find interesting examples and tutorials on the Paper53 blog and website.
There are tons of examples of drawings made on Paper on the web, and tutorials, too. Here's one that features examples made with the first version of the app, it's much more versatile now, with a full palette of colors and blending tools available.