I was looking at the 580EX II with instant rebate on Amazon.com, and I noticed that if you purchase it with the PocketWizard PWP-TR 801-125 PLUS II Transceiver (Black) you get 10% off the PW ($20 savings).
So the final price is:
$370.00 = 580EXII: $420 - $50 IR
$169.20 = PW 801-125: $188 - 10%
$539.20 ($68.80 savings)
tax and shipping may apply for some, but none for me (prime + live in CA)