The Reddit one is fun. They work on a freemium model- the basic service is free but you can pay for some fun additional functions. For example, you can "roll" t

The Reddit one is fun. They work on a freemium model- the basic service is free but you can pay for some fun additional functions. For example, you can "roll" to give a semi-random tip. My favorite extra function is that you can use "internets" to tip bitcents. "+5 internets verify" will send 0.05 BC to the recipient. Cracks me up.