Lernu!

lernu! is a multilingual, web-based free project for promoting and teaching Esperanto. The name "Lernu" comes from the imperative form of the Esperanto verb "lerni", meaning "to learn". The site is run by E@I, an international youth organization, which started as a working group of the World Esperanto Youth Organisation.
The site's content includes various tools for learning Esperanto, such as exercises, games, dictionaries, grammatical overviews, an examination system and a multimedia library with books, music, voice-narrated stories and videos. The site also provides communication services such as an instant messenger, discussion forums on various topics, and news about Esperanto events. Esperantists and Esperanto organizations can advertise their activities and services on the website.
Statistics show the website being visited nearly 75 thousand times per month. Most of the visitors come from Europe, South-East Asia and both Americas.
History.
The "lernu!" project was first proposed at the first Esperanto@Interreto (now E@I) seminar in Stockholm, Sweden in April 2000, and was developed in October 2001 at the second seminar of E@I, in Uppsala. In July 2002, the project received monetary support from the American Esperantic Studies Foundation (ESF), and work on the website started in August of the same year. It was publicly launched on 21 December 2002, and from then on has been supervised and developed by E@I with the ESF support and the help from many individual supporters and assistants.
During four years of the project's development, several people contributed. The core team was responsible for the overall supervision and development of "lernu!". It was assisted by several designers and programmers. Dozens of translators used a specially-made online translation system to make the website available in more than 20 languages.
Courses.
There are multiple courses on the website, ranging from simple word learning (Bildoj kaj Demandoj) to difficult rewriting of stories (Kio okazas)