On the reddit AppNana page you will find hundreds of valid codes each day. Since you need to wait until five friends have entered your code it's a good idea to post your own code on the AppNana reddit page as well.
Beware: the number of posts in reddit is restricted. You cannot post your own code all day. Also there are strict post rules; make sure you read them first.
Another tip: make sure you have read my tips to gain dozens of Appnana referrals.
Make sure to use my code n6215050 and wishing you many AppNana's!