The main area of controversy in homeopathy is around the issue of dilutions, but many people do not realise that there is a great deal about water we still do not understand. I have mentioned this in previous blogs, see Weirdness of Water and Avogadro for more info and I won't go into it all again here. John Benneth has also talked about dilutions on his blog and has reviewed the research which has been done for over a century to try and understand why homeopathically prepared dilutions are still measurable and have an effect on cells, bacteria, plants, animals and humans.
I came across a video on Oasis HD which shows how unexpectedly water can behave. The same sample of water can produce different images when handled by different people, or can be affected by a flower.
On a similar theme, here is a short video of some of Dr Emoto's work on ice crystals.
A much longer video about Dr Emoto and his work can be found here.