<p>I have some configuration values for an asp.net web app.  They will be maintained by a system admin once the system goes live.  Should I store these values in the database or in a config file?  Is there a best practice for this sort of thing?</p>

Depending on the context of the config information, you could choose to leave it in the web.config or you could create maintenance tables for it in the database. I would typcially keep things more backend specific, like connection strings, ftp locations, usernames/passwords(for the application, not user permissions) in the web.config though.
I normally keep more relative information that relates to the information in the database rather than the application itself, in the database.
This is all loosely based though and not always the case.