Have you seen Scholarpedia?
It is a wiki project on scientific subjects that are written by experts of the field and are peer reviewed by others. It means that you will know who is actually writing the most part of an article, and you know s/he is an expert.
The project is in its infancy now, so you probably cannot find the subject you like to read about, but there are several authors promising to dedicate an article to it (and the good point is that I know many of them – maybe just because they are really big figures). Currently, three main subjects are covered: Computational Intelligence, Computational Neuroscience, and Dynamical System.
This idea looks interesting to me, but I am not completely certain if it goes very well or not. The potential strength of such a Wiki project comparing to usual edited volumes is their self-sustainablity generated by people’s continual contribution. Because of rather strict conditions to start writing an article (I cannot contribute a new article unless I am really known in the field), and because of the difficulty of editing current articles (your edits should be approved by the curator of the article), I believe that the dynamics of the system is close to a damping one. I do not say these properties are bad. Actually, they bring some strength to the project (i.e. quality of experts), but they have some negative impacts too.
Whether Scholarpedia will continue to grow or just converge to a fixed point(!) is not clear to me. We may need two years to be able to predict its fate. (;
If people continue to expand this project for the next, say, 10 years, it would be a great human project. Though if it needs a constant push from its original editors, the project will not be *so* special anymore.
The other problem with the project is that it is copyrighted! I don’t like it personally, but maybe it is the best choice.
All said, I hope this project goes on well and cover other subjects of science too.