Here's mine. It's a combination of ideas from others in this thread and my own tweaking; basically, the idea is to generate fort sites that have everything -- trees, magma, sand, water, flux, adamantine, evil good AND neutral biomes, etc. After a lot of tweaking, I've generated about ten worlds with this template. Every map had a site that was at least useable, if not perfect (i.e., no sand, or the adamantine and volcano were too far apart, etc.), and i've found a couple that were excellent.
[WORLD_GEN]
[TITLE:WORKIN]
[DIM:257:257]
[END_YEAR:1050]
[BEAST_END_YEAR:2:50]
[END_YEAR:1050]
[REVEAL_ALL_HISTORY:1]
[CULL_HISTORICAL_FIGURES:1]
[ELEVATION:200:325:800:800]
[RAINFALL:0:100:1600:1600]
[TEMPERATURE:45:55:200:200]
[DRAINAGE:0:100:400:400]
[VOLCANISM:40:100:1600:1600]
[SAVAGERY:40:66:1600:1600]
[ELEVATION_FREQUENCY:1:1:1:1:1:1]
[RAIN_FREQUENCY:1:1:1:1:1:1]
[DRAINAGE_FREQUENCY:1:1:1:1:1:1]
[TEMPERATURE_FREQUENCY:1:1:1:1:1:1]
[SAVAGERY_FREQUENCY:1:1:1:1:1:1]
[VOLCANISM_FREQUENCY:1:1:1:1:1:1]
[GOOD_SQ_COUNTS:1000:4000:20000]
[EVIL_SQ_COUNTS:2000:4000:20000]
[PEAK_NUMBER_MIN:0]
[OCEAN_EDGE_MIN:0]
[VOLCANO_MIN:200]
[REGION_COUNTS:SWAMP:0:0:0]
[REGION_COUNTS:DESERT:0:0:0]
[REGION_COUNTS:FOREST:0:0:0]
[REGION_COUNTS:MOUNTAINS:0:0:0]
[REGION_COUNTS:OCEAN:0:0:0]
[REGION_COUNTS:GLACIER:0:0:0]
[REGION_COUNTS:TUNDRA:0:0:0]
[REGION_COUNTS:GRASSLAND:0:0:0]
[REGION_COUNTS:HILLS:0:0:0]
[EROSION_CYCLE_COUNT:1]
[RIVER_MINS:800:800]
[PERIODICALLY_ERODE_EXTREMES:0]
[OROGRAPHIC_PRECIPITATION:1]
[SUBREGION_MAX:5000]
[CAVE_MAX_SIZE:500]
[MOUNTAIN_CAVE_MIN:800]
[NON_MOUNTAIN_CAVE_MIN:100]
[ALL_CAVES_VISIBLE:1]
[TOTAL_CIV_NUMBER:100]
[TOTAL_CIV_POPULATION:20000]
[PLAYABLE_CIVILIZATION_REQUIRED:1]
[ELEVATION_RANGES:0:0:0]
[RAIN_RANGES:0:0:0]
[DRAINAGE_RANGES:0:0:0]
[SAVAGERY_RANGES:0:0:0]
[VOLCANISM_RANGES:0:0:0]
Savagery is restricted to a middle range so that you'll primarily get haunted/wilderness/mirthful biomes (largely because I had problems with giant skeletal eagle infestations in the first few good locations I generated). Temperature is restricted to (mostly) temperate, with some cold edges. Megabeast levels are set high because I want megabeast attacks, so the history will only run 50 or so years.
One thing about this set is that it walks very close to a few borders -- sometimes you'll get a "too many subregions' rejection even though I have that set to the maximum of 5000, sometimes you'll get an error because there aren't enough squares left to make as many evil/good squares as desired, sometimes there won't be enough room to place civilizations. But you shouldn't get more than one or two rejections.