Software Freedom Day
"SFD is a worldwide celebration of Free and Open Source Software (FOSS). Our goal in this celebration is to educate the worldwide public about the benefits of using high quality FOSS in education, in government, at home, and in business -- in short, everywhere! The non-profit organization Software Freedom International coordinates SFD at a global level, providing support, giveaways and a point of collaboration, but volunteer teams around the world organize the local SFD events to impact their own communities."
More details at http://www.softwarefreedomday.org/