I'll second Park Tools - my all time favorite tool is the Park MT-1. Its a tiny all arounder that will do most of the basic adjustments you ever need on the road (I only wish it had a spoke wrench incorporated - I think they could do it!) It also has a little flat head screwdriver that is really useful for picking glass out of tires. Wrap a bit of duct tape around the handle and you can fix nearly anything on the road. (ask me how I know.... we even taped up a broken spoke of mine once - it didn't really fix the wheel, but it did let me limp the bike home)