Alchemy Open Source sketching

Alchemy is an Open Source, cross-platform drawing and sketching software. It is not CorelDRAW or Illustrator, but it is also not Photoshop. However, it has a nice mixture of vectors and bitmaps, a minimalistic interface, some effects which makes it worthwhile to sketch on a computer instead of scanning hand-drawn sketches.

All in all, it is really worth the try. There are effects such as mirror, distort, pull, generate shapes etc..

Also strange: no undo, no real editing. You just keep on sketching and overpainting. End results can be saved, obviously.

Give it a try.