it also depends on where you are. i can be a hundred + miles from a bike shop here in new mexico. i take along an extra brake & extra shifter cable. 2 sets of brake pads (3 now since 1 is about to go). extra quick release for my bob trailer. emergency spoke.
someone mentioned hose clamps for emergency repairs on this site at one point. a dollar bill, or something usable as a "boot" for your tire.
since i travel with a bob, i bring a stand-up pump with a pressure gauge on it, as well as a hand pump for in the city riding, if i take the bob off.
along with the questions nugget asked,
where will you be travelling? the above stuff are things i take along, but i camp everywhere, and try to be completely self reliant..barring some extreme emergency.