Somewhere (I can't remember where) I came across a McLinkerson to the library libnoise, a noise-related library I hadn't seen before despite my extensive googling. It's actually pretty decent, and I like the way the library chains various classes to create a sort of noise cascade. You attach sources and modifiers together in sequence, then simply call GetValue() from the last in the sequence to get the final noise value for a 3-tuple input coordinate. Modifiers include blending and selecting, scaling, clamping, etc... Pretty nifty. The library includes a demo application that procedurally generates an entire planet from chained noise sequences, which is by anybody's standard way cool. It's got oceans, rivers, badlands, plains... you name it. They've got a sequence diagram showing how the modules are chained together that is pretty informative. Some really cool stuff. Check it out

So, I've sort of retired my current (fairly crude) perlin noise generation stuff to the background, and have written code to expose the libnoise modules to Lua. Works pretty well, I just need to write the final simple glue code to build heightmap and tilemap buffers from final noise outputs. Easy as caek. Or pi, whichever you prefer. I like the way the library was designed specifically with this chaining method in mind; it makes some of the stuff I do quite a bit simpler.