Prescription drugs and Insurance

I spend way too much time looking at various insurance things. Today I shall be reading about health insurances and drug coverage like medicare part d. Personally, we have Aetna health insurance and, while it's not particularly good coverage, it does cover prescription drugs. (Though, for some reason, insurance companies have decided that birth control prescriptions don't really need to be covered so the out-of-pocket fees for those are higher.) Mostly I'm just curious about what Medicare will and won't cover. No real reason why I'm curious. I guess it's just interesting information to have handy.