Go to the main Amazon App Store
page. Above the free app of the day is a small banner "Verizon Connection Day" which has a big long ugly URL, which probably has all sorts of stuff in it that I'm not supposed to post here.
It looks like the promotion pages are still being worked on. It includes free songs (both normal and Prime) and free apps as well as the
Audible offer. When I first went to the page, the songs showed up but the apps section was blank. After I "bought" some of the songs, I reloaded the page to see if the apps would show. Instead, the normal songs disappeared and the only things showing were the Prime songs and the Audible offer.
The Audible $10 credit offer gave me an error the first time I tried it, but succeeded the second time.