Now that Psionics Unleashed is out by Dreamscarred Press, Pathfinder looks like a very friendly option. Plus, the Piazza has a 3e/Pf friendly Dark Sun discussion going.
Not trying to start some sort of system/edition war here, but could you please expand on this? What makes it better than the rules put out by them for 3.5, or the Psychic's Handbook by Green Ronin, or any of the other psionics stuff kicking around for 3.x? For a fair number of folks out there "Pathfinder" really isn't different from "3.5", despite whatever tweaks that fans might happen to like/prefer. Your quote above seems to suggest that Psionics Unleashed is better and I'm wondering if that's a preference (you like Pathfinder) or if there's some sort of significant reworking of the Psionics Unleashed rules making them better than any of the other 3.x psionics.
Thanks.
Oh and since it appears I didn't actually offer up a system myself...I thought sure I had...
4th Ed Talislanta. You can find it here:
Talislanta Library
The rules are actually pretty straight forward. Even if you don't happen to care for the setting (which I also really dig), the rules should do you just fine for what you're looking for. Won't cost you a dime either, since the owner of Talislanta has authorized all the books to be posted up; his way of thanking folks for their support of Talislanta over the years.
Magic is probably going to be where you'll need to spend a bit of time thinking, but the Codex Magicus should help out there.
You can probably get some inspiration for some of your Dark Sun stuff too by downloading the "People & Places: Djaffa" book.
The Menagerie (either d20 version of Tal version) should provide you with some additional funky critters if you want to spice up your Dark Sun game. While I personally feel the d20 version of the Tal rules is far less than it could be, it should be at least mildly helpful in figuring out stats if you stick with a d20-based game.
One of the big things about 4th Ed Tal is that it runs on an archetype sort of character generation. Meaning you page through the book, find an interesting looking picture or turn to the area that the game is happening in and pick it, tweak a few points to customize it to the player's desire, and you're good to go. You can literally have an entire group of people have characters all done and ready to go within less than half an hour; most of the time being spent in trying to decide which archetype you want to use.
What I'd suggest doing is looking through the archetypes and simply "reskin" them to match the particular "class" and "race" combos you're looking for. For example, the "Thrall" (the tattooed dude stabbing the critter on the cover of the 4th Ed book) might do just fine for a Mul warrior type. So, go through the book, grab a bunch of archetypes, and when someone says, "Yeah, I want to be a [whatever]" you'll be able to just give them the archetype you've picked and you're good to go.