Forum Moderators: phranque
Hundreds of them. Maybe thousands. There are innumerable "host review" sites, but many of them have serious problems in that there's no way to verify the validity of reviews -- there are many incidents of "stuffing the ballot box."
There are also "host rating" sites, but the problem with many of those is that they're quietly owned and operated by a hosting company (so in effect they're rating themselves and their competitors), or in other cases what appear to be ratings on merit are actually pay-for-position ads -- so you have to do some investigation on those.
There are plenty of hosting-related forums as well, which might be the best bet because you can engage in conversation with past and current customers and perhaps the hosting companies' representatives themselves. A search for something like "web hosting forum" at Google would probably bring you the best-known and biggest of those.