If there is one company in the aftermarket that has a broad spectrum of aftermarket parts it is Eaton, Not only does Eaton make superchargers and hosing, but the company has a large line of some of the most popular rear differentials for racing and street cars. The Eaton diffs are very strong and ensure that you get the power your engine is making to the ground.
Eaton has a nice YouTube video that explains how one of the more popular differentials, the Detroit Locker, operates. This particular rear diff is popular because it will ensure that both of the tires on the rear of your car keep turning at the same speed even if one of those wheels is in the air.
http://www.youtube.com/watch?v=FYBOoljH-qE
Additionally it will allow the speed of your wheels to vary around corners for better handling and less clunking and is made for a wide variety of applications. The Detroit Locker is surprisingly simple with few parts, which is one of the reasons it is so robust and effective. Check out the video to see how the Detroit locker works and how simple the diff really is.