Mobile sign up screen: Songpop’s sign up screen offers a bonus for facebook sign ups (preferred way to sign up), you may sign up using an email address and you may well start playing without even signing up. 

Dropbox referrals: as far as I know Dropbox has been one of the earliest heavy users of great referral bonuses. Let’s take another look. Here’s a view of all the (official) ways to top up your account, on top you can upgrade right away.

Freebie: Hipmunk (@thehipmunk) is giving away a bonus level for Angry Birds. Merry Christmas everyone.