This offer appears to be only for those with the new Kindle Touch (at least, that's the only one of mine where it showed up).
Buy an Android smartphone from AmazonWireless & get a $25 Amazon Appstore for Android credit
Click on offer, then click on the link on the offer page to receive an email with the offer details. Sign-up for this offer expires on December 2.
Limit one offer per customer and per device.
There is no promotion code for this one - you click to get the offer sent to your email and if you buy a qualifying phone by January 2, 2012, using the same Amazon account, you'll get the credit, no later than February 2, 2012 (I suspect they delay by 30 days to account for those who return items; if you return the phone, you lose the credit).