Since 1999, the SkyscraperPage Forum has been one of the most active skyscraper enthusiast communities on the web. The global membership discusses development news and construction activity on projects from around the world, alongside discussions on urban design, architecture, transportation and many other topics. SkyscraperPage.com also features unique skyscraper diagrams, a database of construction activity, and publishes popular skyscraper posters.
I stumbled upon this site today, and thought it was hilarious. I know it's not skyscraper related or anything, but this is the only forum I'm a member of that is local enough for this to make sense to a good number of users.