According to Videogamer.com (linked above), the first Fallout 3 DLC dubbed 'Broken Steel' will be hitting the PS3 on September 24, 2009... followed by Operation: Anchorage and The Pitt on October 1st.
To quote: "Bethesda has announced that a new update for Fallout 3 on PS3 was released today, addressing a number of issues, implementing some optimizations and adding trophy support for the upcoming DLC.
Good timing too, with Bethesda also confirming that the first of five upcoming DLC releases, Broken Steel, is to be released on September 24.
This will be followed by Operation: Anchorage and The Pitt on October 1, and Point Lookout and Mothership Zeta on October 8."
More PlayStation 3 News...