As estimated by the University of Oxford, over 200,000 people from around the world participate in Model United Nations Conferences every year. Below is a list of a few sites which provide extensive links to MUNs around the world, some which even offer online participation.

Global MUNs and Resources

United Nations Cyberschoolbus
Although the United Nations does not offer its own MUN, promotes the MUN movement and gives access to many basic resources. Particularly relevant are their MUN eNews and the global MUN Calendar.

World Federation of the United Nations Associations
This page has some basic information on MUNs and links to MUNs organized by United Nations Associations around the world.

Model United Nations (MUN) of the United Nations Association of the United States of America (UNA-USA)
This page has a global MUN calendar, which may be the most useful tool to find out if there is any upcoming MUN close to your place. You can also sumbit your own conference information for being added to the calendar. It also have an interesting newsletter, called "The Delegate", with background articles and interviews or opinion pieces by diplomats and politicians.

The Hague International Model United Nations [Netherlands] by the THIMUN Foundations This is one of the biggest MUNs of a global scale, with around 3,800 participants from all around the world. It is held in the City of The Hague, the city of international law. The Conference is held in English. Their page has a Link section to many other MUNCs that are associated with the THIMUN.

MINU Internet Model United Nations.
A forum-based international MUN.

United Nations OnLine
An iternet based international MUN.