gedunk once bubbled...
I know of people/LDS selling the PADI Scuba Diver course in a one weekend format but none selling the full OW course in a one weekend format. I don't teach the Scuba Diver course but you could get through that material in one weekend if you wanted to.
I have seen several places in the orlando, FL that offer the full OW course in two days. I have also spoken to severl instructors that do private classes that offer two day courses. (one said he would go as far as cover Nitrox in two days, and throw in a snorkling with Manatees while we were at it, that down right scares me!) One dive shop in Crystal Springs told me that I could have my OW, AOW, and Nitrox in 4 days. Needless to say, that worries me quite alot.
One a side note, this are not all PADI classes. There were also a couple of NAUI instructors that are offering the same thing.