Benadryl:
Erowid Diphenhydramine (Benadryl) Vault
Dramamine:
Erowid Dimenhydrinate (Dramamine) Vault
DXM:
Erowid DXM (Dextromethorphan) Vault
be careful with DXM, it itself is not very dangerous, but many people take cough syrups with other active drugs in them. You can find many brands that have cough syrups with DXM as the ONLY active ingredient.
As has been said before, Erowid.org is one of the best informational resources on the net with the compiling of almost every known recreational drug, or drug with potential for abuse. If you are willing to do the research and understand what you're doing I takes much of the risk out of a lot of drugs that could otherwise be very dangerous.