Depending on where you're going, you might also consider the security of both your bike and stuff. Of course, it probably goes without saying, but make sure to pack extra tubes, Co2 cartridges if you use them, hex wrenches and some lube. I bring an extra folding tire, too.

I forgot to mention that I do bring some snacks and Cytomax. I found some single serving packages of the latter that are handy. The first year I brought a tupperware container of the stuff and the moisture got to it and turned it into solid mass. On tours, no matter how supported they are, I make sure to keep food and cash on me at all times.