AMD's Alex Deucher has today announced the availability of the documentation covering the R600 Family Instruction Set Architecture. This ISA (Instruction Set Architecture) documentation covers the unified shader block found on the Radeon HD 2000/3000 series and newer. This PDF document is 342 pages long and does go into detail surrounding R600 vertex and geometry shaders.
While this document is new to open-source graphics driver programmers, it isn't fresh and written by the Bridgman-Deucher duo. This documentation was originally designed for GPGPU programmers and had originally shipped with the CAL (Compute Abstraction Layer) SDK (for more information on that topic, read AMD Releases Stream SDK For Linux
and AMD Talks About Stream SDK On Linux
If you're a developer and interested in some good documentation reading, head on over to the R600 ISA PDF