Stross has a good Singularity novel, Accelerando.

Vinge has an interesting novel - Marooned in Realtime - that follows a group of humans who missed the Singularity and have been "Left Behind" so to speak. Not Sing Fic, but a neat concept.

Come to think of it, there's a lot of post-Singularity fiction, but very little actual "in the Singularity itself" fiction that comes to mind.

OH! Chiang's short "Understand" is an awesome watching-the-singularity-happen story, and is available here: http://www.infinityplus.co.uk/stories/under.htm (Almost everything Chiang's ever written is brilliant, FWIW)