This section I don't know about as much since it takes so much more work and quite often you need to be fairly poor to be able to enroll in them, but it's always worth a look and doesn't hurt to apply.
Many drug companies offer a variety of patient assistance programs for patients that don't make enough money to afford continually taking the medications which they need. There are a great variety to these programs from company to company, age group, and other factors. Ideally you should go to each medication's website to see what programs are offered in addition to the manufacturer's main website to find programs they offer.
The 2 sites which I find are the best if you don't know how to look for programs or to see the variety of manufacturer programs for your medications are:
Partnership for Prescription Assistance
I always recommend using both sites to make sure you see all programs for your medications. Be prepared to fill out paperwork and go back to the doctor for them to fill out paperwork as well depending on which program and the directions offered.
EXTRA WORK: If you really want to save more money look into county and state services for low-income as well, sometimes counties will have a health plan that you can take part in if you don't make alot of money.