Mass Effect 3's free "Extended Cut" DLC is available now on Xbox 360 worldwide. The PlayStation 3 version should be available in North America when the PSN updates later today, European Shepards on PS3 will need to wait until July 4. We don't have a current time on the PC version's launch. According to BioWare, all three platforms should have it available today, June 26.
The "Extended Cut" DLC addresses the controversy about the game's ending, adding cinematics and epilogues to fill in the space opera's conclusion. Whether it resolves the controversy is another matter entirely.