Since 1999, SkyscraperPage.com's 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.
Also cool: Manhattan, George Washington, Williamsburg, Bayonne, Hell Gate, Akashi Kaikyo (sp?), Menai Strait, Britannia (demolished, sadly), Pont Neuf, Henry Avenue Bridge here in Philly, and the Tunkhannock Viaduct.
The Brooklyn Bridge is probably the awesomest bridge I've ever been across, though.