AT&T, FTW!
But the pricing plan is pretty crappy:
My bill is 54.04 every month (provided I don't go over)
For 450 minutes, 5000 Night/weekend, Rollover, Free calls to AT&T customers (all 50 million of us), and 7 P.M. - 7 A.M. Nights, and 200 texts (I'm over 38 texts this month thanks to ecurbj, you owe me $3.80 :P)
I love Cingular, but I wish I could get free internet too. The 3G on my phone is pretty awesome, but if you don't have a plan it's 1 MB for 10 bucks, lol.