Are you using the word "rating" to mean "impact factor"? If so, most journals broadcase their IF either on their home page, or a quick google check will bring it up. Whether this is a meaningful piece of information is another question.

Interesting question regarding acceptance rate of conferences, although I doubt that a resource exists.

I haven't seen information about acceptance rates at conferences anywhere except in the notification that your paper has been accepted to one of them. This is not restricted to bioinformatics. But I too would be interested in such information, although I have an idea which journals seem more serious than others (and boldly speaking, I always felt that boasting about your journal's impact factor on its front page makes it look more like a holiday trip catalog than anything else).

Of course, those of us who have published at those conferences and possess the information you want could contribute it in another community wiki question.