Important point about the water and snacks - you would be amazed how much this stuff will cost you at the hotels - usually 5 times as much. So if you can bring it, definitely do. This applies to anything that you would normally run to the store for - alcohol, food, cigarettes etc.
Ramster - good point about the moderation - I had one night where I just couldnt stay awake and had to beg off from a really important dinner party - and all because I had a little too much around lunch that day.
Walking shoes definitely - remember the walk to the convention center is over a mile from the hotel inside - or at least it sure seems that way and if you have to go back and forth it can get pretty tiring.
Extra disposable cameras - you never know when a great opportunity will come along and your dig camera just died - or for that matter - if you see any just lying around at parties it is perfectly ethical to use them in camera wars
