Qubes OS Architecture v0.3 (pdf)
Qubes GUI virtualization protocol
Networking in Qubes
Inter-domain file coping
Command execution in VM (and Qubes RPC)
Dynamic memory management in Qubes
Implementation of DisposableVMs
Article about disposable VMs
Implementation of template sharing and updating
Build instructions:
Building Qubes core and gui packages: see this message
KDE Dom0 packages for Qubes
How to build Qubes installation ISO