Recently I learned how to make Photoshop actions and now I cannot stop. This new one is very simple and creates an effect of a cross-processed photograph.
Cross processing technique was discovered by mistake (using the wrong chemicals to process the film), and has been very popular among creative photographers ever since. It changes your photographs in a very interesting and often unpredictable way. Now that we are in the digital era, imitating a cross-processed photograph is as easy as tweaking some curves.
Here is the cross processing action I made for Adobe Photoshop CS3 or CS4. Before you apply the action, make sure that your photograph is in RGB mode. It works best on well exposed high-contrast photographs.
PS: If you do not know how to install actions in Photoshop, here's a really quick tutorial.
Update: I was playing with the action a bit, noticed an interesting effect: applied multiple (3-5) times to the same photograph, it creates a colorful poster-like illustration. It's probably not very useful for the real world, but can be used in collages, etc.