Another of the giants has left us. I read To Your Scattered Bodies Go and some of the Riverworld sequels, and loved them. He was well-known and well-appreciated when he was more prolific, but maybe not so much now.
http://www.pjfarmer.com/

Here are some links about his works:
http://reason.com/blog/show/131886.html
http://hnn.us/blogs/entries/63786.html