On PhillyFuture, dovate maps out a plan for a new Philadelphia subway, which would stretch from Broad Street to Strawberry Mansion, and maybe even into Manayunk.
The great thing is that some of the infrastructure is already in place, from an old viaduct line that runs from the Terminal to the Museum. Of course, this is all just freethinking–a great idea, but one which has very little chance of actually happening.
More Slate stuff: they now have a textcast. A lovely way to use your iPod.
Worldmapper does sweet things with maps of the world.