I like discussions on transit. It's fun to sit around and shoot the breeze about whatever is going on. Here in San Francisco there used to be forums over at the SF Cityscape where the folks would gather to talk about transit, but its migrated over to Ess Eff. Cityscape still has some awesome resources including a huge blogroll.
As forums go though, I don't think there has ever been one about the transit oriented lifestyle but over at the Metro Rider LA Fred Camino and the gang have done just that. So if you want to go talk transit, check it out. And if anyone wants visit Frank up in Seattle and jump start a conversation there, he's got one too, although the comments section to his blog and over at STB are pretty lively. And down in my hometown of Houston Christof and the gang have the CTC forums.
Are there any other transit forums out there? I know there are a number of yahoo groups with epic battles taking place daily between the transit folks and anti-planners/libertarians but I hadn't seen any in other places.