"The problem with intelligent design is that no mechanism by which an external intelligence could influence biological life is offered. The only external source of information or design that I could accept is life being introduced to earth from outer space by way of meteorites. But I find the idea of a nature that is self-organizing much more appealing. Perhaps you could say that nature herself is intelligent. But there is no need for a God, even if one does exist."
I think the problem is that theism is mostly defined as God acting outside of nature in the sense that nature, left alone from an interventionist God, cannot - for the most part - produce the wonderous structures we see in the universe (e.g., galaxies, stars, planets, life, biological intelligence, etc). I think this limited definition of theism is mainly based on the religious traditions of theism where God is intervening in human affairs, and as a result, is seen as acting outside of nature.
However, I don't think there is a conflict between naturalism and supernaturalism. Let's put it this way. If supernaturalism exists, then it is naturalism by definition since naturalism is what ever is 'natural' - that is, exists out of nature, or if you will, exists out of what happens to exist. If God exists, which I believe he does, then God is 'natural' since God exists out of what happens to exist.
The question then, isn't so much whether supernaturalism exists, it is rather, can nature exist in a form that would strike human beings as 'supernatural', that is, beyond the natural occuring things (which is what supernatural literally means)? In this sense, supernaturalism is what human beings have no direct experience and implies a suspension of natural processes and/or laws as we humans perceive them at some point in our evolution.
Of course, there are many natural processes that would have been considered supernatural by our ancestors. The further back in our prehistory we go, the more natural processes appeared as supernatural (e.g., the sun was considered a supernatural object by many of our ancestors).
The question further becomes, are there natural processes that exist that even humans today would consider as 'supernatural? We know that Einstein rejected some aspects of quantum mechanics as spooky science (e.g., entanglement at action at a distance), which is akin to rejecting it for its supernaturalist implications. QM's action at a distance implications are still controversial and they remain controversial because they strike many scientists as 'unnatural'.
When we review processes such as self-organization in stellar and biological evolution, it becomes another matter of scientific dispute whether such processes occur, or at least as a main driver of evolutionary structuring. Nevertheless, again we are at the peripheral edges of what is considered natural science by many.
Carl Sagan once said that God is doing less and less as we learn more about science. Another way of looking at it is that God is more and more becoming a part of science. That is, the more we learn about science, the more we need to expand our scope of what is natural to include those things that at one time would be considered 'spooky' science. As 'spooky' science evolves, so should our understanding of theism.
The main thing is whether this evolving understanding will ever equate God with the current theistic view of a personal God. That is, of course, never going to be known by our generation. There is a long way to go from the laws of quantum entanglement to the kind of supernaturalist God mentioned in religious scriptures.
However, where science can tell us little, mathematics is much more kind. We see in mathematics the hand of God more directly in the sense that it appears 'beautiful' and elegant to even the most atheistic mathematician. Perhaps the most beautiful of all structures is the transcendental constant Pi. Of course, Pi is everywhere in both physics and mathematics. But, what is one of the most bizarre about this apparently random number is that an algorithm was recently discovered called the Bailey-Borwein-Plouffe Pi Algorithm (see http://web.archive.org/web/20010411140022/http://www.mathsoft.com/asolve/plouffe/plouffe.html ).
This formula is significant for theism because it confronts randomness and somehow finds meaning in the most random findings of all mathematical pursuits - the digits of pi. Maybe Euler's argument in the 17th century isn't so far off base (see http://epc.buffalo.edu/authors/hennessey/data/epitome/epilogue.html ).
What better way for nature and supernaturalism to meet? They meet in the same intersection as art and mathematics. The doorstep of God's feet.