As far as I know, this is the only decent live cam of the NE Corridor. Amtrak does not stop at Norwalk, but you can figure out the Norwalk action: For Northbound, add about 10 minutes to Stamford departure; for Southbound, add about 17 minutes to Bridgeport departure. Lots of action from locals, Amtrak NE Corridor, and Acella.
If you know of any other decent NE locations, let me know. I also watch Ashland, VA, which includes the NY/Florida trains, Auto Train, and many freights.