The project you saw at OSCON was called RAIV (Rack And Inventory Viewer). Unfortunately it ran into a dead-end and is currently vapor-ware. Currently we're using an internal CakePHP webapp for basic inventory and customer tracking, but its very buggy and lacks many features.
We are in the midst of working on a completely new project that will cover many of the problems mentioned in this article and beyond. Think of it like an open source datacenter management webapp and backend. Its still in the planning stages, but the intent is to have a plugin based system where you can use the inventory plugin, DNS/DHCP plugin (to replace maintain), virtualization management (deployment and console access), etc all in one interface. The idea is to create an admin interface and a customer interface so that they can access and see information about their environment. We're far from having a demoed project but we hope to have something soon.
Variables don't; constants aren't.