Right now you can get a free $2 credit in the Amazon Android App store when you connect your Twitter account to your Amazon account.  Go to the Amazon.com Twitter offer page then: 

• Connect your Amazon.com and Twitter accounts. If you are not already signed in, you will be prompted to do so.
• Automatically follow @amazonappstore on Twitter. The message "I just got a $2 credit for Android apps from the @amazonappstore. Click http://amzn.to/tweetapps2 to get yours. #get2" will be automatically tweeted from your Twitter account.

 

After completing these steps successfully, browse for apps and games for your Android phone or tablet, and click the "Get now with 1-Click" or "Buy now with 1-Click" button.

 

To confirm the $2 value was applied to your account, from any app detail page click "Redeem a gift card or promotion code & view balance." You should see a popup with your $2 code applied to the "Apps for Android" section.