This $500 rebate is stackable on top of any and all other public offers, and takes only minutes to submit your application (which must be done within 60 days of purchase). Took about a month before I was fully confirmed to be eligible for my Sonata purchase in early May.
Edit: No longer works --> Tip: Use %%%
as the search criteria to return a full listing.
One caveat per terms and conditions:
THE REBATE FOR ANY PURCHASE OR LEASE USING ANY HYUNDAI CIRCLE PROGRAM SHALL BE $100
All credit goes to rsauthor1 in the Hyundai Sonata thread. After confirming that this offer is completely legit I decided it needs to get a lot more exposure vs. staying buried forever in that thread.