The fastest I have heard of a Hub being indexed into GOOGLE search and Yahoo is something like 6 hours or something like that. It might have even been quicker than that. Just cannot seem to remember at this moment, but as the person before me posted, GOOGLE will send it's tools to come and check out your hub and index it.
You can go to pingler.com and ping your hubs for free, and that will bring a few viewers. I recently read on a hub that pingler.com does not help with indexing, but does help to bring traffic.