Dstat is a versatile replacement for vmstat, iostat, netstat, nfsstat and ifstat. Dstat overcomes some of their limitations and adds some extra features, more counters and flexibility. Dstat is handy for monitoring systems during performance tuning tests, benchmarks or troubleshooting.
slurm started as a pppstatus port to FreeBSD. As I ripped off several functions here is an overview of the features:
Full screen ncurses and X11 traceroute tool.mtr combines the functionality of the ‘traceroute' and ‘ping' programs in a single network diagnostic tool.
scponly is an alternative ‘shell' (of sorts) for system administrators who would like to provide access to remote users to both read and write local files without providing any remote execution privileges. Functionally, it is best described as a wrapper to the tried and true ssh suite of applications.
Clam AntiVirus is an open source (GPL) anti-virus toolkit for UNIX, designed especially for e-mail scanning on mail gateways. It provides a number of utilities including a flexible and scalable multi-threaded daemon, a command line scanner and advanced tool for automatic database updates. The core of the package is an anti-virus engine available in a form of shared library.

