Wikipedia is the online encyclopedia that is updated by users. This provides each organization with the opportunity to provide their own information about their mission and activities. Some organizations have taken advantage of the opportunity. Others have not.
If your internet strategy is defined well, updating your wikipedia entry should be part of your regular activity. At least monthly.
For example, take a look at the entry for World Vision. They have done a great job of organizing their entry. It provides a great deal of information about who they are, what they do, and their history. Another great entry is Habitat For Humanity.
An example of a not so great listing is Compassion International.
The platform provides a great opportunity to distribute information about your mission and reason for existence.