Get a free sample of Playtex's "sport tampons"
promoted through Walmart. Just share your name, e-mail, address and date of birth and answer four questions about your tampon use. You can opt in or out of Playtex's e-mail list. The implication is that these tampons are designed to be worn while playing sports, though I've never used them and am not sure how they compare to regular tampons.
It's unclear how long this freebie will be available because the site just says "while supplies last." The free sample takes 4 to 6 weeks to arrive.
Caveats: one per household.