If you want to learn about the new (now on hold) tunnel under the Hudson and the expansion of Penn Station, look here:
http://www.arctunnel.com/
If you want to learn about the now under construction renovation of the Farley Post Office into the so-called Moynihan Station (which, despite its name, isn't a new station, but only a new entrance to the existing platforms of Penn Station), then look here:
http://www.empire.state.ny.us/Subsid...MSDC/MSDC.html
And finally, the redevelopment of MSG is discussed here:
http://www.msg.com/events/transformation