A few years ago I wrote a texture plugin for Blender that creates ripples on water (which can be tweaked in all kinds of ways). It still works in the newest versions of Blender and I have a page about it here:
http://wiki.blender.org/index.php/WaterPlugin
I would love to see more 'texture effects' in Blender. I think there is a lot of potential for new ideas there.
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