A couple more
A very good piece of server monitoring software can be found in Xymon (Hobbit as was). Great for quick glance monitoring state of server farms. Knocks spots off the paid for IBM Tivoli Monitoring.
The other is Webmin which is a great admin tool - you can farm out some administrative tasks easily to people with no special privileges, reducing the danger of people finding ways to circumvent sudo. (Ours was used to allow help desk people to set up printers across platforms without needing to know the quirks of each of the different command lines)