Attached Link: Skyopal (Anita )

There are some great presets for it, including wet paper, wetter, and one of my favorite's Arctic Brush.  It is free!!!

There is another great plugin  and some things to add to it for great results.  Check out Retouch Pro website for presets for both of these and instructions.

Another good thing is Buzz >Simplifier. It quickly removes some detail, as much as you like, light or dark, and makes a photo look like a water color.

Lots of folks like to use Mehdi filters to enhance the edges, whether black or in the colors in the photo, increasing saturation, or outlining in the color of your choice which is super effective.

DC Special also has an Outliner tool with lots of variations . If you have a layer that is outlines, a layer that has been Buzz simplified, a Virtual Painter layer, Impressionist, Paint Engine or any combination of the above, you can create some cool painted effects easily.

Another trick I like to do is simply create a blank layer and dabble different colors of paint with some drybrush or charcoal brush shape and use it as an overlay over your outlined drawing.

Also, add a sandstone texture or a watercolor paper texture for a realistic finish.

These are my personal favorites and if you try them on layers and play around with different opacities and blend modes, you should be able to create lots of 'paintings'.