Check out Artweaver, it looks just like Photoshop! If your out and about looking for a image editor you should give this a try. Artweaver is a simple Freeware program for creative painting, i.e. Artweaver offers you all artistic effects which you need for your work.
You can create sketches from photos and experiment with a wide range of brushes. The brush simulation is thereby so realistic as possible.
Here is the link http://www.artweaver.de/index.php?en_version