Qubes OS Architecture v0.3 (pdf)
Security-critical elements of Qubes OS
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
Dom0 secure update mechanism
Build instructions:
(outdated) Building Qubes core and gui packages: see this message
Building all Qubes packages
KDE Dom0 packages for Qubes
How to build Qubes installation ISO