I would like my body donated to medical science because I will have no further use for it and have discussed this with my family, who have no objections. Once you die, you no longer "own" your body, it belongs to your next of kin and they can dispose of it as they wish (within the law). I have not, however, gone as far as contacting an organisation that might want it, probably because I don't intend to die just yet - but who knows? LOL
If nowhere wants it, then I would quite like a "green" burial with a cardboard coffin. I believe this is the most ecologically sound method.