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.