There are a zillion different bacteria, and not all antibiotics work on them all. If you're even thinking that you might want to keep drugs on hand, look up lists of "most common" organisms as well as the drug of choice for each of them. If you go to a traveler's clinic, they would most likely write you scripts for a few antibiotics as well as instructions on when to use them. As anatess' story illustrates, antibiotics are serious medications and not to be used on a whim.
The most important question to first ask yourself is "why am I keeping these on hand?" For us the answer is "earthquake"- so what type of infections might you get? Skin/Wound infections (and possible sepsis), GI issues due to contaminated water, etc. Given that penicillin allergies aren't too uncommon, and 20% of penicillin-sensitive people cross-react to cephalosporins, I've tried to constrain my drugs to quinolones (not for kids) and macrolides.
Here's a list of antibiotics I keep on hand-
Le coeur a ses raisons, que la raison ne connaît point. On le sent en mille choses. C'est le cœur qui sent Dieu, et non la raison. Voilà ce que c'est que la foi parfaite, Dieu sensible au cœur.