I carry a simple patch kit from Park Tools for this reason. I only carry one tube, and unless there's some disastrous blowout I just patch the tube on the road and then continue on. Before you put a new tube in you've gotta find out why you flatted, so since you're doing that you'll know exactly where the hole is on the tube and it's only a minute to patch it. I've used the self-adhesive type patch for butyl tubes, and for latex tubes I use the vulcanizing type.
Anyway, I too ask if people need help - or at the very least I slow way down to see if they wanna flag me down or say something. Cyclists gotta stick together out there.