Journals vary dramatically in how quick they are to make a first decision, and in how quickly they get accepted articles online and/or in print. E.g. some journals make uncorrected proofs available online within a few days, some have final versions within a few weeks, others can take a few months or more for the article to be available at all.
However, it's often hard to find much information on this, and harder still to find it in a form that allows efficient comparison of a group of journals (cf. the infamous JCR Impact Factor or Google Scholar's journal metrics). Anna Sharman's blog is one of the best sources I've found so far, but is (understandably) far from complete (links below, now updated following the blog's move to cofactorscience.com).
Could this be something that ResearchGate should try to do? E.g. either by asking journals/publishers for information, or by asking authors to "tag" their papers with times for first review and from acceptance to appearance, so that RG can then make journal-level statistics available? This might be unique, and could be far more useful than RG's current project on citations, which seems like it is never going to compete with Google Scholar, Scopus, Web of Science, etc.
http://cofactorscience.com/blog/submission-to-first-decision-time
http://cofactorscience.com/blog/acceptance-to-publication-time
http://cofactorscience.com/blog/surveys-of-journal-speeds-and-decisions