In many states you can check a box on the back of your license indicating that you wish to be an organ donor. There are also organ donor organizations that provide cards. However, for many people, a mere check the box isn't sufficient. When you speak with people about making the commitment if they can more clearly specifiy what the do and don't want to donate, and under what circumstances, more people will tend to make the committment.
Everyone that ventures out in an RV should take along some key medical records and an original signed health care proxy and living will in case there is a problem along the way (and especially if you're full timing). As part of encouraging folks to protect themselves with the correct legal documents you should help eduate and encourage them to become organ donors when they complete their living will and health proxy. It is simple and as you so well point out, can save a life. Too many people get skittish about it or say that their religious beliefs prevent organ donations (that is often not true, religious beliefs do impact some of the details but they rarely prohibit organ donations entirely).
I posted a long explanation of what people should do with living wills and health proxies recently on a thread about first aid (if you really want to be prepared you need the right legal documents, not just band aides). You can find it by searching "health proxies" i think.
There are free forms people can access on
www.laweasy.com (its a free legal site I host). If the samples there don't make the case strong enough or address organ donations let me know and i'll post more forms. If there is a way to give samples people on airforums can use i'd be happy to do that as well.
If there is a better way to advocate this noble goal on airforums let me know and i'd be happy to help.
I'll be posting a new thread on how we'll be using our Airstream travels to promote similar health causes, chronic illness in particular (Diabetes mentioned by one of you is certainly a major one). Perhaps our paths or goals will overlap. Let me know if you have any suggestions.