XnSketch is an interesting tool which makes it quick and easy to turn regular digital photos into works of art. We looked at the Windows version, but it's also available for OS X, Linux, iOS and Android.
Open your source image and you can apply one of 22 effects by clicking its thumbnail at the bottom of the screen. There are pastel and sketch options, cartoons, halftones, print and stamp options, and more. And as you click each one so the XnSketch preview window immediately updates to show you its results.
If you're not quite happy with an effect then you can tune it by adjusting various settings. These always include brightness, contrast, gamma, exposure and saturation, but some effects provide additional options: edges, colours, opacity, blur and so on.
XnSketch still isn't quite as capable as some other graphics tools. "Oil Painting" is such a popular effect elsewhere that we were sure XnSketch would deliver great results, for instance, but actually it proved disappointing. And there aren't enough dedicated configuration options to help. Yes, the program lets you play with colours and brightness, but we wanted to increase the brush size, amplifying the effect, and there's no way to do that.
Still, other effects do deliver much better results. When you're finished, you can save the results as a JPG or PNG file, or share them via Facebook, TwitPic, Flickr, Picasa, email or a host of storage providers. And this can be a surprisingly quick process: click File > Share > Imgur, for example, and there's nothing else to enter or do. XnSketch just uploads your current image, then opens a web page to display it, and all you have to do is share that URL with whoever you like.