I may be embarking on a project involving a fairly extensive healthcare records data set, looking for the use of a particular type of drug (for example, "Proton Pump Inhibitors"). But these drugs are usually listed by their trade or generic names - is there a well maintained resource for looking up what drugs are members of a certain class (if class is indeed the right word)?
Also, if you have $900 sitting around, you can get a subscription for the United States Pharmacopeia. I'm not sure if that can be spread across multiple subscriptions for an organization like the Red Book David mentions.
It's free to use anywhere (even on a mobile device) by anyone in your organization ... after you pay the subscription fee. The fee for research is much less than the fee for commercial use.