Hi, we needed new wiki so that the languages could be separated and links could be added between language versions of the same article; also this wiki should not be a storage of worksheets (we have http://www.geogebra.org for that), but rather a collection of information about geogebra (manual, tutorials). Some worksheets from the old wiki are now available on GeoGebra, but we didn't move it systematically. Old wiki is still available, but new users cannot join. For sure we don't want to move the whole old wiki to the new one.
If you want to help, you can think of a tutorial and add it to Tutorial:Main Page. Some hints for contributing to this wiki in HowTo. Or you can browse through the wiki and help us find manual articles that are too brief and help us expand them using the public part of the article.