I'm managing Linux servers for my team. For each new instance, I install the following softwares:

• etckeeper which keeps tracks of every changes in /etc
• shorewall to have a simple setup for firewall
• rsnapshot which keep incremental backup of important directories
• cron-apt: which take charge of update of the system (or, in my case, send me an email to warn me about new updates)

But I was wondering if you administrators have any other wonderful tools for daily management. I'm not talking about remote management (like cfengine) but little tools which help to manage a small number of Linux servers.