Normally, I don't make announcements about software, but this is a pretty cool system that onki wrote to me about:
phpReview is aiming to be a complete Free Reviewing system, entirely based on PHP. Originally made for book-reviews for the NL.Linux.org site it will be redesigned to be a general reviewing system, including voting, reactions and about anything else found in a good reviewing system. It will be licenced GPL.
If want to take a look and see what it's all about, check out this link and get all the info.