There appears to be a bit of a debate gearing up over at this thread on homeopathy and its effectiveness. Check it out and get involved, in the name of evidence-based rationality.
All I can say is that pro-homeopathic people tend to have rather interesting special pleading for the ability of water. Apparently you can dilute an active medicine so much that it is simply not there, but water can remember, somehow, that active ingredient, and, hey presto, it works.
Which is amazing, because water must have selective memory. It seems to be able to forget shit and piss and viruses and bacteria and disease and pestilence and dirt and assorted crap that it has also been in contact with.
Clever water! Like magic
Except less plausible.