Heya Doozer!
I keep a few tampons in my kit but mostly pads because they can be used as wound dressing.
As for "the keeper" thing that Mike suggested,well...
it's a bit of an icky little device,but i have tried it(yup,I'm female!), and the one thing that you should do if you plan on adding it to an emergency kit ,is to practice using it a couple of times first. It can be a little tricky,and the last thing that you need in an emergency situation is to worry about leaking. *ahem* (sorry guys).
The good thing about "the keeper" is that it is reusable and can last for years.However if you are allergic to latex do NOT use it.