Packing for Destination Weddings

I get asked a lot about how I pack for a destination wedding.  In order to have the proper back up equipment, I am usually packing at least two cameras, two flashes, multiple lenses, batteries, memory cards, and I need to make sure everything fits on the plane under the seat in front of me.  When Carin travels with me for a wedding she brings a nearly identical bag so we essentially have four of everything.