UCADay, or Ubuntu Community Appreciation Day, is a special day for Ubuntu Community to thank each other for using or participating to it. It’s on November 20th every year and it’s coined to be a feast for all members of this great community, that’s why it’s just once a year and not every 6 month, after each release, that’s because it’s about the community itself, not about the distro alone, it’s really a feast for the whole community to thank each and every one for supporting it, either by using or somehow contributing to it, and every contribution counts.
It’s easy, jump to some IRC channel, mail your LoCo’s mailing list, phone some loco colleague, meet with some users, hold some event, you can use even Facebook, twitter, identi.ca, just to say Thank You! to everyone contributed something to this community and don’t forget to Thank your self
More here: https://wiki.ubuntu.com/UCADay