On Aug 31, 2012 SpaceX conducted a full wet dress rehearsal (WDR) for its scheduled Oct 8 2012 08:12 PM EST launch of SPX-1, its first fully operational cargo Dragon resupply mission to the ISS.
In a WDR the Falcon 9 is rolled out, fueled and the countdown run down to the very moment before engine ignition. Then the tanks are drained, the F9 is rolled back to the hangar and everything is checked out. Later another rehearsal will include a "hot-fire" - a 3-4 second engine burn to check them out too. This usually tales place a few days before launch. During the recent WDR the Dragon and its cargo trunk were not attached, but they likely will be for the hot-fire.
Non-ISS cargo for this flight will include a prototype ORBCOMM OG2 communications satellite built by Sierra Nevada Corp. (also builders of the Dream Chaser spaceplane.) If all goes well 17 more ORBCOMM's will be lofted on later F9 flights.
This will be the next to last flight for the Falcon 9 v1.0 before the much larger and powerful Falcon 9 v1.1 comes into service. The F9 v1.1 will also be the core stage of the monster Falcon Heavy.