Endura Stealth is my favorite. It is spendy but you can find them on sale if you have time to shop. I have two, bought one at a Beaverton Bike Gallary sale in 2010 for $150 and another in 2011 for the same price.

The Stealth has both side and pit zips. Here is video showing the features.

http://www.youtube.com/watch?v=SswGHDjZhoA