Have you seen this Facebook app to support the positive psychology exercise “Three Good Things”? Participants in this exercise record Three Good Things, and the reasons why they happen, every day. There are some other versions of this exercise out there (including an iPhone app and one on happier.com), but this is a way to make these exercises more effective using social interaction.
This app is at http://apps.facebook.com/threegoodthings/, but the page with more info is at http://www.facebook.com/apps/application.php?id=119352832576&v=info. It is free to use, but because it is research, they ask participants to complete very brief surveys after 1 week, 1 month, 3 months, and 6 months of use.
This could be a great way to spread your own happiness.