Various way to mimic painting with Gimp

Gimp is this open source application that is a pseudo Photoshop - and it has many features, from photo editing to image retouching, or even painting

Here are a few of the filters available that would turn a photo in a fake painting
Distort Filters : Value Propagate
Filters/Artistic/Oilify
Filters/GMIC/Artistic/Painting
Filters/GMIC/Artistic/Kuwahara
FX-Foundry/Artistic/Water Paint Effect

Here is the forum explaining a few tricks and some tutorials
http://www.flickr.com/groups/gimpusers/discuss/72157619108510544/

A proper tutorial to emulate smudged painting
http://www.gimpusers.com/tutorials/smudge-painting-technique

And last but not least the online website to test some filters
https://gmicol.greyc.fr/