Ralph
Ralph is an asset management system for your data center. It lets you see what hardware and software is installed. It also lets you keep track of who is using every device, for what, and how much it costs.
Ralph's database can be accessed through a web interface, a RESTful API and through command line tools, the most important of which is the discovery command, which lets Ralph gather information about your data center automatically. You can also export and import parts of the database into different formats.