I'm just recently back into cycling, so here is a somewhat naive question - what do you carry with you on a trip of say 5 miles or more?

By that, I mean do you guys carry any tools, tubes or anything else that might be of help should you break down or get a flat on the road? And if you do bring anything, what do you feel is the best way to carry these things? Saddle bags, backpacks etc...

I ask because I used to ride a MTB around the neighborhood for excercise, so it wasn't a big deal should something happen, but I've recently bought a road bike and I am going further these days as my endurance increases. So I would hate to be stuck to far from any help.

Thanks!