The Wikipedia article about gripe sites:
http://en.wikipedia.org/wiki/Gripe_site

Another list of gripe sites (along with some helpful information about starting your own):
http://www.webgripesites.com/

An interesting piece about how at least some lawyers are realizing the pointlessness of threatening or suing the operators of gripe sites, noting that most of them are completely legal:
http://www.techdirt.com/articles/20090405/1832594397.shtml

From the other side of the fence, a company trying to sell a service to shut down gripe sites (worth a read):
http://www.hostingdude.com/internet_complaint_sites/stop_internet_complaint_sites.htm

Another interesting article about gripe sites in general:
http://www.associatedcontent.com/article/60685/gripe_sites_when_something_sucks_post.html

If you have a gripe and want to air it out, we can help you.  I can host your gripe site as a subdomain for little or no cost!

If you have a simple site, with a couple static HTML pages and images, I’ll host you on a subdirectory or subdomain of reallysucks.net for no cost at all.  There are a few ground rules though: Slander and Libel are not supported.  If it is fact, back up your facts.  If it is not fact then it is opinion, state it as so.  I am a huge believer in free speech, I will support you even if I disagree with the company you’re griping about.  I will not allow you to slander or libel someone on my dime   No inciting violence.  A protest is fine. Saying “let’s burn them to the ground and make them pay” is not.

That’s it for now.  I’ll post a lot later as time permits.