Condoms are the best way to prevent STD's.
Even if the woman is on the pill, it's still a good idea to wear a condom every time you have sex. In fact, we stress this quite a bit. In the era of raging sexually transmitted diseases and infections it's more important then ever to protect yourself. Pregnancy is never completely unavoidable with the pill but adding the additional protection to the mix gives you a little more confidence knowing that your 1 night stand or steady lover won't be anything more then that. If you share vibrators we also urge you to put a one over the surface for the same reasons that you should wear a one for sex.