#1) The world of the Blood. Basically, set in the world this story is set in. It's a modern sci-fi/"gothic-punk" type world with competing groups of super-powered psychics etc. It's also a proper Amber game - characters are all built with 5 pts (15 if you give me a character before the con). New powers allowed, strict reading of the DRPG sorcery rules (so you really need to have conjuration to be a decent sorceror), selling down of attributes is expected - compared to a normal human, Amber level strength is pretty mighty.
PCs have never heard of Amber, or Chaos, so there's no Pattern or Logrus. The population of people with Amberite blood is at least in the hundreds, possibly in the low thousands.
The PCs work for the Order of the Grail, a group of humans similar to Watchers (both the Highlander and the Buffy versions) who try to guide members of the Blood to fight evil and keep powerful artifacts out of the wrong hands.
#2) The Nano-Victorian Future It's 100+ years in the future. The world came to the brink of the Singularity, then fell apart. The US has pulled itself back together into something that resembles, in many ways, Victorian England. Except with nanotech, genetically engineered warrior angels and cybernetic implants. The Nano-Victorian Future closes the loop between cyberpunk and steampunk.
PCs can be anarchist proles, gentleman nano-engineers, aristocrats in SmartFibre frock coats and genetically enhanced super-soldiers.
#3) Caecern; a game of high fantasy. This would be the hardest to do as a con game, since the setting is actually pretty detailed, and mostly in my own head. I suspect I'd get frustrated trying to get the player concepts to fit into the not-quite-D&D setting. On the other hand, I really like the setting, and have a very clear idea of how all the powers work.
The upside is, hey, epic fantasy! The downside is that it'd be a high "homework" game for both me and the players. Really I should run this one in an ongoing F2F campagin, but I don't have the time. If I had a handful of players who were interested enough to go back and read some of the microfic, and I got my butt in gear to clean up some of the web info I have on the setting, it could still work.