Short answer: No, there is none.
Longer answer: Learn an interesting skills that can be offered online, then offer the service and accept BTC as payment.
What do you say? Isn't earning bitcoin through the likes of signature campaigns, tweets and posts really boring? I really think so, at least its not an attractive or appealing way to earn bitcoin or any money for that matter.
What do you think? What are the most interesting and appealing ways to earn Bitcoin Online?