“A Gradient Tutorial” on the 9rules site actually explains some finer points of gradients and it struck a chord with me.  I cannot tell you how many times I’ve made drastically contrasted gradients and been sorely disappointed with them — this article fills the gaps.

Here’s a site I’ve never found before and an absolute gem of a tutorial.

I found a few Andy Warhol-esque tutorials while searching for good information on HDR (of which there is not much).

Photoshop Tutorial: How to Create Andy Warhol Inspired Pop Art

Andy-Warhol-Up Your Photographs

Only because this next one is free I won’t bother to say how much it sucks.

Photoshop Serigraphs — remember though the only thing wrong with this technique (in my opinion) is that it is limited by the artist — which could be you.

Additional Links:

http://www.fotoview.nl/

Disabling mouse trails in your operating system preferences can alleviate numerous problems, not just this one.

http://www.iconico.com/discussions/view.aspx?id=2544&forum=8