Last year, I tried out some Photoshop plugins from TwisingPixels. My 7-yr-old PC had a tough time with some of the rendering, but I really liked the effects, though I didn’t spend enough time with the package to really get a grip on flexibility.
They have a free package you can download, called PixelSampler. The two coolest effects are the Black and White filter, and Tonal Streak. The 2nd one has some nifty algorithms that vary a blur distance based on local brightness.
If you are in to plugins, give these guys a try – I especially like the sky rendering stuff they have. I typically do not bother with plugins of any kind, but TwistingPixels is on my short list, and the only plugins I have currently (though I plan to get a few for image correction and sharpening).