I've just read about this and can't believe that I've never heard of this (or thought of it myself) before. The amount saved by cutting the monthly payment in half and making it every 2 weeks is incredible.
I see it applied to mortgages but not to car payments, credit cards, etc. What's the deal with this?
Here are a couple interesting reads:
http://mortgage-x.com/library/biweekly.asp
http://www.mortgage-helper.com/biweekly.html