Insty had a post last week which linked to both an article about the importance of shooting with consistent accuracy, and the MantisX training system.
Yes to the first, and WTF to the second. ($150?)
I am way too much of a Cheap Bastard to use a sophisticated thing like the MantisX. Instead, I use a much simpler (and much cheaper) system:
Feel free to copy. It works at any distance.