This one is pretty quick & easy, if you have a Citi credit card of any sort.
Read about the deal HERE.
Worked for me on the very first try! But then I tried to sign my wife up (on my same iPhone) under her account and I couldn't get it to work after refreshing MANY times. So this is a YMMV. But, if it works, it's a quick/easy $10 Amazon credit.