If you and your dog are facing an amputation, or have just gone through one, you need to join Tripawds, the community website for three legged dogs and cats.
Dogs dealing with osteosarcoma or any other cancer that may require an amputation can really be helped by this incredible community. Their free library of resources are awesome, their discussion forums are invaluable, and their general optimistic, supportive attitude is heaven-sent. They make gear recommendations, review books, and generally make life easier (and more reassuring) for anyone dealing with amputation. They even have a toll-free support helpline.
And if you want to make a contribution to a charity in memory of your own pup, their foundation is a great way to help others in need.