If you are using a prescription from your own doctor, you can go to various websites and compare current prescription prices. For example, I can buy my blood pressure meds from CVS Online much cheaper than the local CVS store.
If you decide to order online, I would highly suggest using a well known, established pharmacy (such as CVS, Walgreens, etc). Some "cheap" online pharmacies have been known to provide pills that are outdated, wrong dosages, contaminated, or counterfeit.
I'm closing this thread because it will attract spammers, I'm sorry!