General server overview

We recently acquired another company that has a few RHEL 4/5 servers.  The support people have moved on to other opportunities, so while we have logins, we have little documentation on what these servers do or where they are related to security patches, etc.

In addition to last login, general hardware and disk configuration, chkconfig list and rpm list, what other information would you target to get a general idea of the configuration?

Without being able to connect to RHN, it there a way to find out what patches may have been applied (a default log)?

Thank you,

Dave