Why is there something rather than nothing?

The latest issue of Skeptic magazine (vol. 13, no. 2, 2007, pp. 28-39) has an article by Robert Lawrence Kuhn which supplies a nice list of possible explanations for the answer to the question "Why is there something rather than nothing?" The article, titled "Why This Universe? Toward a Taxonomy of Possible Explanations" (PDF), briefly sets out descriptions of each explanation, but the meat of the article is found in the footnotes, which provide extensive references for each offered explanation.

Here's the list, minus the footnotes and descriptions:

1. One Universe Models
1.1 Meaningless Question
1.2 Brute Fact
1.3 Necessary/Only Way
1.4 Almost Necessary/Limited Ways
1.5 Temporal Selection
1.6 Self Explaining

2. Multiple Universes
2.1 Multiverse by Disconnected Regions (Spatial)
2.2 Multiverse by Cycles (Temporal)
2.3 Multiverse by Sequential Selection (Temporal)
2.4 Multiverse by String Theory (with Minuscule Extra Dimensions)
2.5 Multiverse by Large Extra Dimensions
2.6 Multiverse by Quantum Branching or Selection
2.7 Multiverse by Mathematics
2.8 Multiverse by All Possibilities

3. Nonphysical Causes
3.1 Theistic Person
3.2 Ultimate Mind
3.3 Deistic First Cause
3.4 Pantheistic Substance
3.5 Spirit Realms
3.6 Consciousness as Cause
3.7 Being and Non-Being as Cause
3.8 Abstract Objects / Platonic Forms as Cause
3.9 Principle or Feature of Sufficient Power

4. Illusions
4.1 Idealism
4.2 Simulation in Actual Reality
4.3 Simulation in Virtual Reality
4.4 Solipsism

One of the most entertaining philosophical books I've ever read was David Lewis' On the plurality of worlds (pretty much everything Lewis wrote was entertaining as well as brilliant), which falls in category 2.8 (Multiverse by All Possibilities), cited by Kahn in note 43. The same category includes another very entertaining philosophy book, Robert Nozick's Philosophical Explanations, which is cited in note 44.

This taxonomy shows that there are a lot more possibilities than "God did it."

UPDATE: Thanks to John Lynch at stranger fruit, who pointed out that the article is available online.