Mom and pseudosister - waited 6 hours.
TTC threads - waited 12 hours.
March DDC - waited 4 days. (that's today - HI!)
MDC in general - I'd say next week, but I'm going to be gone, sooo...

Mid July?
The rest of my family - dunno, I'm thinking of using this as an excuse to host Thanksgiving, so I guess whenever that question pops up.

Otherwise, we're definitely waiting for as long as we can manage. Fortunately, we don't live in the same state.
The rest of my friends - Whenever I happen to show up with either an obviously pregnant belly or a baby in tow, they'll know. I'm cruel like that.
Random people I don't really know - when it becomes obvious enough that they comment on it.
If I weren't on TTC threads at the time, I would have waited to tell anyone for at least a week, and I now think I should have waited on telling anyone but TTCers for at least that long. Ah well.