I just tested the Moodle Wiki. Wow, I am sorry but I simply must share this with the whole world. It is Excellent...
OK, there might be bugs, I am not issueing any guarantees ;-)

It is an easy to use tool in which groups of students can build there own hyperlinked set of knowledge. And it is not restricted to text either. Other students can watch it develop and you can review the popularity of your own weblog as it grows.
So let them [grow] using a Wiki. Now all I need is an enthousiastic teacher.