In a good Blizzard tradition, "soon" is set as the date for when commodities will arrive at the RMAH. Gold, however, will not be available until later moment.
Community manager Cerunya wrote:
"The following commodities will be available for trading in the real-money auction house:
- Crafting Materials
- Blacksmithing Plans and Jeweler Designs
- Pages of Training
The ability to trade gold as a community won't be included in this initial update, but we hope to enable it in the near future. Keep an eye on this thread for further updates."