Thanks, great suggestions.
waldronate, that's starting to look a little closer to Jiggle.
It occurs to me I should explain what I'm hoping to use it for. I'm not worried about coastlines, though all of these techniques would work well for them. I'm thinking more along the lines of breaking up forest or other regional textures so they blend together better. I'm angling for a map style somewhere between a "typical" map-like representation and something closer to aerial imagery. So clean or simply faded/blurred edges don't really work.
One of the tutorials I read made use of this technique quite effectively. Though, of course I can't remember which one at the moment.
I've used difference clouds in some cases, as well as ocean ripple, sometimes even working it by hand (especially with forests). For the most part it has worked out okay, but some situations I just really wish I had a 64-bit Jiggle.