The following post is a modified version of a reading list I posted to Amazon some time ago. I found each of these books to be absolutely fantastic. If you're at all interested in pondering the future of humanity, I would highly recommend reading all of them in the order presented here.
A good starting point is The Age of Missing Information. In the early 1990s, author, Bill McKibbon, had an entire day's cable programming recorded. This included 24 hours of each channel, totalling over 1700 hours of broadcasting. Over the following months, he watched it all. This book contains his reflections on what kinds of information television provides us and what it lacks. He compares what we learn from TV to the kind of information he is exposed to on a day of camping in the woods. And he reflects on the differences in the types and quantity of knowledge available to pretelevision generations as opposed to contemporary people, providing a good reflection on where we are today.
Next read Pale Blue Dot: A Vision of the Human Future in Space by Carl Sagan. This book was first published in 1994 but is still very current, because sadly, very little has been done in space since it was written. Sagan is very thorough. He discusses everything that has been achieved thus far in terms of spacetravel and exploration. He speculates about what will be possible in the future and the sorts of technologies that need to be developed. He gives a complete inventory of the solar system, including planets, moons, asteroids, and the Oort Cloud and what they have to offer future space travelers, both in terms of practical uses as well as intriguing unanswered scietific questions. He discusses encountering extraterrestrial life, both intelligent and not as well as travel between the stars in the distant future. There are many interesting tidbits here that you won't find anywhere else.
The third book on this list will absolutely blow your mind. It's The Age of Spiritual Machines: When Computers Exceed Human Intelligence by Ray Kurzweil. It explores the consequences of Moore's law (the observation that computer processing power doubles every 18 months) for the 21st century. Kurzweil argues that not only will computer power continue to increase exponentially throughout the next 100 years, but the rate of increase itself will probably increase. By 2099 there will be no distinction between human and computer intelligences. The vast majority of humanity will inhabit a completely virtual world in which our mental processes are accelerated a millionfold, and everyone is essentially immortal. I know it sounds like another crackpot book, but check it out anyway; the arguments are quite sound, and Kurzweil is a recognized technologist.
The Clock of the Long Now: Time and Responsibility: The Ideas Behind the World's Slowest Computer by Stewart Brand takes a much longer view of the future than Kurzweil. Brand is involved in a project to construct the world's first 10,000 year clock, a timepiece that, with occasional maintenance, will keep time for the next 100 centuries. The rationale is that such a project will influence people to take a much less shortsighted view of the future and consider how actions taken today may impact the distant future. The point is made that the effort required to effect change is usually directly proportional to how far in advance a change is attempted. This is especially relevant to environmental issues.
Now conclude your reading with Reason for Hope: A Spiritual Journey by Jane Goodall. In her latest autobiographical book, Goodall writes that people are often surprised and even skeptical when she tells them that she is hopeful about the future. This book is her answer to them. She reflects on her life from early childhood to her work in Africa, first with Leaky and then on her own, studying and working with chimpanzees, to her current environmental and educational work. She draws on evidence from her life experiences to argue that despite the frightening and precarious state the world is now in, she believes that humanity will ultimately have a bright future. (Why is it that half my posts turn out to be ape-related?)
Also of note is The Transparent Society: Will Technology Force Us to Choose Between Privacy and Freedom? I haven't read it yet, but based on the fact that it's by David Brin and was well-reviewed on Amazon, it's definitely a contender for this list.
On the web you can check out David Brin's essays about the future and Ray Kurzweil's enormous site dedicated to future technologies.
Happy reading!