Everyone knows Wikipedia, but you may not have run into Wikitravel yet. Check it out – I wasn’t aware of it till today, though it appears to have been around for a couple years already. Still, it’s not yet nearly as comprehensive as Wikipedia yet, and might offer some opportunities to write some articles.
Neat.
Looking at my home town I must say that telling tourists to go mauka or makai without actually telling them what those words mean is a little mean.
There fixed that.
p.s. I now have my own wiki for my genealogy. What fun!
I was just about to start a thread on this but did a Search first and found this one. I only heard about Wikitravel today. An update is here. They already have guides to Chicago and Singapore.
Oh, and I mean Chicago and Singapore are printed books for sale. I think the OP was referring only to online guides.
Well, if anyone wanted to know about microbreweries in San Francisco, I can proudly say that Wikitravel is now quite the valid source. 
Being a Kiwi, I naturally headed over to the New Zealand page, just to see what they said about us. Very good stuff, indeed! 
This should be a big help to travellers.