I found this free plugin which seemed very good. I can't post links but it's called "wordpress review engine" and it's from a site called "wpeden". I installed it in a couple of WP sites I have but it isn't working for me. Whenever I create a review and publish it, when I want to view it it shows a blank post. When I use the shortcode for creating a page with a list of all the reviews, I see that the links to the reviews work, but it uses another type of permalink which is different from the one I gave the review. Well, it may be complicated to understand the problem just by reading it, but I thought maybe some people here were using the plugin and could tell me if it's working for them. Or if you haven't and are interested, you could also try installing it and telling your experience here. I have posted my problem in the WP support, but who knows how long will it take for the author to answer.