Shell Programming and Scripting

I am curious to know what kind of cron-jobs experienced admins have running on their servers.
I personally have :
1) something to backup very regularly my important directories
2) something that build (at night) my software under development
3) something that build (at night) my Docbook own and personal documentation
4) nothing to monitor the state and health of my system and this is in this domain that I would love you to shed some light.
5) any other useful tool you can think of!
Thank you for your help and keep up the good work!

Depends what you have on your servers, I suppose all those using cron and having RDBMS installed schedule the shutdown of DB in order to take backups and start again after...
I personally reinitialize all smb stuff at 23:00, clean all temporary directories at 21:00 etc... on some boxes I clean and clear users and stop TP mode so the box can enter in batch mode but before all has to be backuped etc...

Important jobs I tend to run on most server include.

Checking and report via email/SMS alerts when:

1) Free disk space goes below certain threasholds.
2) A Spooled print job takes more than 30-40mins to print
3) serious entries appear in database log files (eg data corruption messages)
4) Hardware fault conditions detected by OS (eg failed disks in RAID, Power supply failure and the like)

Typical maintenance jobs:

1) Backups (system, files, on-line database)
2) Log file rotation
3) Purge or archive old data eg spool files, wtmp logs
4) capture of sar performance counters
5) Terminate dead user sessions/network connections