The Internet provides many opportunities to disseminate educational materials free of charge. One of my favorite technologies are wikis. Wikis allow a selected group of people or anybody to collaborate on a set of documents. The most popular wiki is Wikipedia. Here are some useful ESL wikis.
Curriki is a curriculum-based wiki. It markets itself as a Global Education Learning Community. Click here to view some ESL materials. Curriki also contains course materials for other subjects.
WikiBooks is part of Wikipedia. This site provides books in the wiki-style; a collaborative effort by many people. Here are some ESLwiki books.
Wikiversity is also part of Wikipedia. This site uses the wiki concept for online teaching. Click here for ESL-related materials.