DrugBank is an all-in-one resource for patients and healthcare providers alike to look up detailed chemical, pharmaceutical, medical and molecular biological information on nearly 4,100 drugs. I looked up a couple common headache drugs and am impressed with the results: Topamax, Vicodin (which brings up results for acetaminophen since it is one component of Vicodin) and Imitrex. It also links to popular drug sites, including Drugs.com and RX List, for when readers want more information.
via ChronicBabe