I just discovered this great tool called Wikibu. Wikibu is an initiative and research project form the Zentrum für Bildungsinformatik of the Pädagogischen Hochschule PHBern in Switzerland. It is only available for the German Wikipedia, but it looks promising.
The principle is quite simple (well, it might be technically difficult, but that's another story): its goal is to rate the potential quality of Wikipedia articles on a few objective markers, including:
- Number of visits
- Number of authors having participated to the construction of the article
- Number of backlinks within Wikipedia
- Number of sources used in the article 
It also takes into account whether the article is being heavily worked on, and if the discussion page is being used, which allows to see if the topic is either "hot in the news" or maybe "heavily discussed" due to disagreements. It also takes into account the ratings given by the Wikipedia Community (good article - lesenswert- or a featured article - exzellenter Artikel). Wikibu also lists the different authors of the article, assessing their participation in writing it.
Finally, it lists the necessary links to the different pages of the article (discussion, history) and a link which prompts to work on the article, as an incentive to make it better.
Wikibu is meant to be a tool for education. It does not pretend to be able to rate the quality of the content, but rather aims at giving a few pointers as to what makes a potentially good article in Wikipedia. Based on statistical analysis, it provides a good starting point to evaluate the content and most important, gives a good overview of how an article is built, taking into account the most symptomatic pieces of the community process and making them clear for readers who might not know where to look for discussion or authors.
I am looking forward to seeing it extended to other wikipedias, I think it can help both the readers and the contributors to look at Wikipedia in a different way.
See below the ratings on the article "Dolphin" in the German Wikipedia.