The observance of World Press Freedom Day started in 1993 with the proclamation by the UN General Assembly (source).
Throughout the world, 3 May serves as an occasion to inform the public of violations of the right to freedom of expression and as a reminder that many journalists brave death or jail to bring people their daily news.
The theme of World Press Freedom Day 2006 is the correlation between media freedom and the eradication of poverty (source).
See this page for more information.
Thanks to Incommunicado for suggesting this post.