Passwd_exp notifies users via email of upcoming password or account expiration. Its simple modular architecture allows you to perform expiration checks on any data source you use (SQL databases, LDAP...), send expiration warnings only to desired users or group and on selected days only. Administrators can use it to review expired accounts in the system. Support for Linux and Solaris shadow (including LDAP and NIS systems) and BSD passwd systems is included.
Rogue Detect sends DHCPDISCOVER packets to the network and listens for DHCP servers to respond. It can run continuously as a daemon, or do a single probe and quit. It's written in Perl and can be easily extended to take any action you can think of in response to an unknown DHCP server (send pages, disable them, etc).
OpenSMART is a monitoring (and reporting) environment for servers and applications in a network. Its main features are a nice Web front end, monitored servers requiring only a Perl installation, XML configuration, and good documentation. It is easy to write more checks. Supported platforms are Linux, HP/UX, Solaris, AIX, *BSD, and Windows (only as a client).