RackTables is a tool to manage tens of racks, hundreds of servers, and thousands of MAC and IP addresses. It will work with a single rack as well. It features a real-life rackspace model, typed rack objects with flexible attribute sets, a tagging system, IP address management ready for NAT, virtual routers and load balancers, accurate network connection handling, a universal search function, a multi-user access model, and an extensible dictionary.
MachDB is machine database to catalog of the changing state of your hosts. It consists of a database, an aggregator, an XML spec, and some example information gathering scripts. Along with a Web UI, these form the basis of a system that will allow you to catalog the current and historical state of the hosts in your infrastructure. It has been designed with scale in mind, and the goal is to support 10k hosts. It is being actively developed and is used in production at a few organizations.