Do you know Rotten Tomatoes? It’s a review aggregator which measures the percentage of positive reviews of most films. I think it’s really helpful if you want to watch a film without knowing anything about it (except a number), which can sometimes be vital (see 12 Monkeys). Thanks to it, I discovered Win Win (94%), El secreto de sus ojos (91%) or the documentary Exit Through the Gift Shop (96%), and I narrowly escaped Hereafter (46%) or Nine (37%). There are some subjective false positives though, like Norwegian Wood in my case (74% while I hated it).
When I’m looking for film showtimes, I always use Google Movies rather than AlloCiné, because it gets to the point (no posters, no ads, no useless slideshows, just showtimes).
I made a bookmarklet which catapults Rotten Tomatoes ratings into a Google Movies page. It uses the Rotten Tomatoes API, which is great (you need to register as a developer to get an API key) and jQuery.
Here is a quick example, put your mouse over this image:
As you can see, not all films are recognized by the API, and some ratings may not be available yet.
If you want to try it yourself, bookmark this link, go to this page, and click the bookmark.