I have my 72 hour kit in a rolling backpack.  After watching the evacuation of New Orleans prior to Hurricane Katrina I realized I might not always need to carry it on my back.  I would rather pull it behind me.  Pulling would also be easier for kids.  Keep in mind, 72 hour kits do not need to be elaborate and you do need to be able to carry them, just in case!

The link to the left is a sample 72 hour kit list.  A good place to start if you haven't already.

Don't stop preparing at 72 hour kits, you also need car kits, work kits, school kits, etc.  It is prudent to have multiple kits specializing in their intended use.  Don't forget ATV's, snowmobiles, etc.