David Ziser is one of the best wedding photographers working today. He also is a wonderful presenter and his Digital Wake-Up Call is must-attend event (Buffalo, NY is usually on his regular tour schedule). Today on his blog site, David has links to a great video on what exactly goes into professional shooting camera bag. This is an 18-minute video but if you want to know what camera equipment a pro carries to a wedding this is a great video.
BTW David is very much one of the good guys in the photography game. He is most generous with his time and his Digital Wakeup Call Workshop will blow your mind.