Regarding the Category: GURPS idea - I largely see Tempest as a D&D setting. I don't think a D&D setting is much of a system-independent setting. Too many D&D assumptions. For example, in my depiction of Reshen I suggested a plot-hook based on the reincarnation spell and its ramifications for Reshen's society - is this mechanics or fluff?
Since I see the setting as a D&D setting, I suggest "boxing in" rules issues in side-bars rather than putting them in seperate links, for ease of reading. Support for alternate rulesets, if any, could be put in as links. (Is it possible to create collapsable links, that open up when you click on them or something? That would work best, for all rulesets.)
Legally, I am not sure how you intend to support GURPS, for example. Putting GURPS mechanics into the wiki would, IMO, be not legal or at least shady. Likewise for Ars Magica or whatever. Barring OGC or other open systems (True20, Fudge...), and I mean really open ones (not Iron Heroes, for example), I would personally prefer to stay very clear of such murky legal waters.
I really like the new maps. They may be less eye-catching, but they are very clear and just what I think is needed. The new open-source format is also a very good idea. (I use Firefox too.)
The climate-maps were a great thing, I would love to see them reworked into the new format. (The only problem I had with them was that I am a bit color-blind, and found some of the colors hard to distinguish.) I would also like to see a map with D&D-environment defitions however ("this area is Cold Mountains, this is Warm Forests..."). Perhaps I'll try to master the program and work on something like that based on the current climate maps.
I liked the guidelines. They form a good summary of, well, the setting.
I suggest adding the last section in the wikis front page to the guidelines page. The guidelines page should contain all of the guidelines, including the notes on the OGC.
I like the Geography page, but I would suggest making the first paragraph less technical, and a little thicker in detail.
The section opens with a very general section, which is great. However, it talks in degrees and latitudes which mean very little to me and, I suspect, to most any reader. I suggest that instead the analogy-system would be used. "Brennan is roughly the size of North America and Gerin is roughly the size of Australia." is a great sentence. Saying "Brennan is a wide continent that spans a diverse climate from an ice cap at its north to jungles at the south", however, works better for me than "these two continents span roughly 70 degrees of latitude" [I hope I remember the climates right]. What about changing the first paragraph to something more like:
The Tempest Campaign Setting encompasses two continents: the large continent of Brennan and the smaller continent Gerin. Brennan is roughly the size of North America and is a large and diverse continent with a climate ranging from an eternal ice cap at the far north to jungles at the south, and with many cultures, kingdoms, and fallen empires. Gerin is roughly the size of Australia, a northern and smaller continent that is almost entirely cold (although not permantnly frozen, excepting its eastern mountains).
A blank latitude/longitude map with mountains, rivers and coastline can be found here. Five degrees of lattitude or longitude on this map is roughly equal to 345 miles.
Something like that? (I'm sure I've got things a bit wrong, but I think in terms of style it works better when it's less technical.)
I like the overall organization of the page. Very clear, and good categories. Excellent. (Of course, we still need to add the small descriptions, and the more detailed wiki entries.)