Software for Tracking System Configuration Changes?

DingleyDon asks: "I am currently administering a growing Unix environment and am interested in better documenting changes such as upgrades, software installs, configuration changes, etc. to the hardware and software on those servers from a SysAdmin's point of view. Obviously, this could be done with something as simple as a text file stored on each system, or a spreadsheet, or any other number of ways. But what I envision is a database app (web-enabled) where I can easily keep all of this information in a centralized location and query on the history of any given server. Is there any such package out there? (free=even better!) What do other SysAdmins use to document changes made to their environment?"