If you want a fictional account of a post-singularity world, you can do no better than Greg Egan's Disapora: http://www.amazon.com/Diaspora-Greg-Egan/dp/0061057983

Not only is it a highly detailed and well thought out vision of the possibilities and philosophical challenges of "living in a computer," but the plot is driven and defined by hard physics. Do not underestimate how literally I mean this last sentence :)

The opening chapter is available free as a short story. In fact I think I will submit it right now.

edit: here we are: http://gregegan.customer.netspace.net.au/DIASPORA/01/Orphano...