BRL-CAD is a powerful constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing support for rendering and geometric analysis, path-tracing for realistic image synthesis, network distributed framebuffer support, and image and signal-processing tools.
ethstats is a script that quickly measures network device throughput. It works by parsing the /proc/net/dev file that the Linux kernel maintains, and thus utilizes a negligible amount of CPU time. ethstats shows the throughput of each device in both megabits per second and packets per second.
bytecounter is a program that copies data while showing a status line indicating the data rate and estimated time remaining. Optionally, it retries on errors, which is useful for recovering files from bad media. It designed to be used "in-between" two programs to measure rate of data flow, such as between the output of a tar command and a file. It works with files, floppy disks, hard disks, terminals, tapes, CD-ROMs, FIFOs, and anything else you can think of.
Nettion (NETwork TestIng and Operational eNvironment) is a framework for developing, deploying, and executing network performance tests, designed particularly for mobile ad-hoc networks. It is distinguished by not using control "backchannels" to start and stop the test, but rather using either a local setup network, the test network itself, or compact flash memory.