Here is a list of some random software I use for the majority of things I deal with:
Zenoss – Open Source Network Monitoring, takes nagios and cacti to another level. Very customizable, but takes a while to become familiar with the system. The more I play with Zenoss, I constantly come across new features and advanced functions.
Monitoring Terminal Services sessions:
Monitoring SQL locks:
Dekiwiki – Open source WIKI, with very good media integration and built-in support for Active Directory. I prefer it over MediaWIKI.