Use the free App from the App Store called Speechcloud Voice Dialer. You say the name and it looks up the name from Contacts so you can choose to dial.
Not 100% hands free voice dialing since you still have to interact with the iphone.
At least you don't need to tap in numbers or scroll through Contacts.
I tried this speechcloud voice dialer when I first got my phone a few days ago. I did not like it. Not sure why? Maybe I'll try it again. I guess I'm very disappointed that after enjoying voice dial with Verizon for no extra cost, I found out after coming to ATT that I didn't have it. NYS also has a law about cell phones and driving. I bought the bluetooth earphone b/c the one I had at Verizon wouldn't work with the iphone. And then I realized I had not voice dial capabilities. HOWEVER ATT doesn't have a problem with adding it for another 4.99/month!!! That is to me, after all the extra I am spending with this new phone, is more than disappointing.