"Accelerando" by Charles Stross

I just finished reading Charlie Stross' (autopope) Accelerando (entirely legally downloaded from his website). It is, pretty much, an update of Simak's old City taking the Vingean Singularity into account. It follows a family from the near future into a not-so-distant future where the majority of the species has changed into something Other. It's probably a fairly good introduction to transhumanist thought.

And if nothing else it has one wonderfully ominous sentence:

We should've known better than to keep upgrading the cat.