Have you seen this segment of word processors? They blank the entire screen and cut you off from everything except word processing.
Guess what they look exactly like. Yeah, that's right, your favorite text editor in a command line interface. How did you know?
I've found that if I ever need to get something done, the best way to do so is to kill X and drop to the command line, fire up MOC for some quiet music in a second terminal, and then open up vi or nano and just do the darn work.
There's no secret to being productive. There's no wonderful application that will fix your problems and make you concentrate. Hunting for a new task manager on the internet kind of misses the point, and perhaps Lifehacker's new tip of the day doesn't make you more productive after all.
It's a matter of turning off the graphical interface, turning off the cell phone, turning off the IM, and just doing the work.