Sketchbook Pro is a professional grade digital sketchbook. It offers a number of brushes and tools that give the illustration created a natural feel. It is easy to use and along with the use of a graphics tablet can quickly allow for the mock up of a visual concept or can be used in the creation of storyboards for a audio visual production.

It also comes as an app that can be used on android tablets or the ipad offering flexibility in order to suit your work flow methods.

Inkscape is an open-source vector based imaging programme similar to Adobe Illustrator, Corel Draw, Freehand, or Xara X.

Sumo Paint is a free online Flash-based image editor that works in a web browser, without needing to install anything on your device.

It has functionality similar to Photoshop and offers many of the same tools but is focused on illustration rather than photo editing.

Sumo Paint offers community features such as uploading, commenting, and rating images for users who create free accounts.

The paid pro version of the software features a downloadable version of the software which runs on Adobe AIR.

Sumo API allows you to embed Sumo Apps to your site. You can integrate Sumo API for free for non-commercial use.

Paid subscriptions allow access to the downloadable editor, increased image resolution, enhanced customer support, and early access to new features.

Sumo is planning on releasing a photo editor in the near future.