I wrote an exporter for blender models that works great for meshes. I'm attempting to extend that to bones defined in blender. However I haven't found good information for exporting bone data. How can I access bone data? I'd like access all the vertices that the bone affects, the weight of each vertex and the matrix. Do I need to export anything else for skeletal animation and dynamic dismemberment?
My suggestion is honestly just to find a format that Blender will export its bones as well, and then look through the script of that format exporter. I was doing something similar and realized how much of a pain it was to find a good resource on exporting bones.
But here's this specification that helped me a lot, on armature modules
@Michael directed me to an excellent resource for exporting bones from Blender. It provides all the information I needed. It's actually already built into Blender, it's the DirectX Model Format.
Go to user preferences, addon section, "Import-Export" category and install "DirectX Model Format (.x)". Then use File->Export to select the newly added format.
This format exports not only the mesh information (vertices, triangles, quads, textures, etc), but also exports armature information, including the armature structure (parent/child relationships), transform matrices, which vertices are included in each bone and even the bone weights for each vertex. Animation sequences are exported too.
All in a human readable ASCII format, so it's easy to write an importer. Beautiful.
The IQM (Inter-Quake Model) format has a set of Blender exporters that will export skinned meshes with blend weights and the armature. Look to http://lee.fov120.com/iqm/ for documentation and code. You could also look at the Doom 3 format MD5 exporters.