Waiting for activation this may take some time

Are you positive you have wireless coverage where you're trying to activate your phone? If so, try turning your phone off, remove the sim, wait ~30 seconds, then pop the sim back in, turn your phone back on.

Who's your carrier? Can you make phone calls?

In my experience, I don't always get a 2nd conformation message saying "iPhone has been activated." So if you can make phone calls, your iPhone is activated.

If not, give us some more information so we can help. =)

There's something wrong on the carriers end; that or your phones a dud(which I doubt). Call or go into a local store.

I get the 'No Service' thing on my old iPhone 3G that has a old (deactivated) SIM card. It's possible that the carrier see's your device but is denying you on their network for some strange reason?

(FYI it only took 10 seconds to activate my iPhone 4 the first time I powered it on.)

Call your carrier.

I am having the exact same problem but with Optus. Activated it online on Sunday Night, Sim Card is in the slot and it's been over 2 days but nothing's happened, still no service.

Oh yeah, except when I put my Sim Card in it didn't say waiting for activation?

iPhone activations can take up to 48 hours. If it has been more than 48 hours, take your iPhone into a local Apple Retail Store or AT&T Store.

48 hours? o_0