Serve is giving away $10 for answering a trivia question. The catch is that you then need to either have a Serve account or need to sign up for one in order to get the funds. This is available in the U.S. only.
Once you have the funds in your account they can be sent to any other Serve user, spent using the Serve prepaid debit card, or withdrawn to a bank account.
How Serve works and why it is relevant to Bitcoiners was described shortly after its April Launch
This promotioin is similar to Dwolla's giveway program earlier this year where amounts from $1 to $5 were given away. Over a decade ago, PayPal (then x.com) gained a user base by offering the same deal -- $10 for signing up.