I had the chance to catch Brent Ozar's webcast last week on creating a poor man's CMDB. In it he talked at length about the Central Management Server feature in SQL 2008. While I use SSMS 2008 my only SQL 2008 database installs so far are running inside Virtual PCs that aren't always on. Fortunately, there is another option – SQL 2008 Express. It's lightweight, free, and best of all it can be used as a CMS. The only catch is that if you put your install on anything other than your local machine (which you're going to do since you're using it as a CMS, otherwise what's the point?) you'll have to enable remote connections. No worries, it's actually an easy task to do – just follow these step by step instructions and you'll be all set.
Update – It didn't take me long after I posted this to realize that there are cases for running SQL Express locally in order to take advantage of a CMS. One example is if you frequently run multi-server queries and you want to create logical groups of servers where a server belongs to more than one group. Another is if you're a one person shop and you want to use Brent's CMDB scripts to gather data.
That makes me wonder, though – why didn't Microsoft just add the ability to register a server in more than one group into Object Explorer in the first place? Hmm, I smell a Connect request cooking!