If you've never heard of Wikipedia then this will be very useful information, as there's no better place on the web that I know of to get free information and learn more about any topic.
Wikipedia is a free content encyclopedia written collaboratively by people from all around the world. If a site is a wiki, that means that anyone can edit articles, simply by clicking on the edit this page link. It runs on MediaWiki software.
There's a great Wiki on Nauru with lots of contributing authors and fresh up-to-date content about this former tax haven.
The Republic of Nauru (pronounced nah-OO-roo), formerly known as Pleasant Island, is an island republic in the South Pacific Ocean. It is the world's smallest independent republic both in terms of population and land area.
Much of its past prosperity derived from the large amount of phosphate deposits on the island, believed by one school of thought to be of guano origin but by another to be of marine origin. The phosphate is used as a fertilizer around the world and the majority of it has been exported to Australia. With the exhaustion of the phosphate supplies, Nauru faces an uncertain future. In the 1990's, it tried to gain new sources of income by introducing itself as a tax haven, but this story came to an end in July 2004.
Source: Wikipedia

