Is there a place to review journals or conferences?
There are a few sites that do this:


SciRev
Journalysis. 
HelpMePublish. 


Of these, I think SciRev is the most active, but I'm not certain about this. That said, in my experience, the actual rating information on these is not of much value. Uptake is pretty slow, and most of the reviews I've seem to just very high marks indiscriminately. As a result, you can't infer too much from the tiny sample sizes available. The information about time to result, review quality, etc. might be useful in principle, but in practice again you've got tiny sample sizes and probably a selection bias as well in terms of who submits reviews -- though I don't know which way this selection bias would go. 

Nature wrote a news piece (not paywalled) about these sites in early 2015.