Highly available Central Administration
One of the common mistakes that I see regularly when architecting SharePoint Farms 2007 or 2010 is the fact that there is only ever 1 server in the farm that has the Central Administration site configured. In these situations you have just created a single point of failure (the very thing we try to avoid when architecting any enterprise solution) in your SharePoint farm. If any thing were to happen to the server running Central Admin you would have no way of accessing the Central Admin to perform any needed admin taks. BIG PROBLEM!!!!
The following articles discuss this very problem and the steps to resolve the issue along with some great tips to making it work as expected.
From the SharePoint From the Field Blog
And another from Spencer Harbar who provides even more detail.