BusyBox combines tiny versions of many common UNIX utilities into a single small executable. It provides minimalist replacements for most of the utilities you usually find in GNU fileutils, shellutils, etc. The utilities in BusyBox generally have fewer options than their full-featured GNU cousins; however, the options that are included provide the expected functionality and behave very much like their GNU counterparts. BusyBox provides a fairly complete POSIX environment for any small or embedded system.
cdrtools (formerly cdrecord) creates home-burned CDs/DVDs with a CDR/CDRW/DVD/BluRay recorder. It works as a burn engine for several applications. It supports CD/DVD/BD recorders from many different vendors; all SCSI-3/mmc- and ATAPI/mmc-compliant drives should also work. Supported features include IDE/ATAPI, parallel port, and SCSI drives; audio CDs, data CDs, and mixed CDs; full multi-session support; CD-RWs, DVD-R/-RW, DVD+R/+RW, BD-R/BD-RE; and TAO, DAO, RAW, and human-readable error messages. cdrtools includes remote SCSI support and can access local or remote CD/DVD/BD writers.
daemon turns other processes into daemons. There are many tedious tasks that need to be performed to correctly set up a daemon process; daemon performs these tasks for other processes. This is useful for writing daemons in languages other than C, C++, or Perl (e.g. sh, Java). If you want to write daemons in languages that can link against C functions (e.g. C, C++), see libslack, which contains the core functionality of daemon.
divine will use ARP requests to look for hosts that are always up in the networks that you frequently use your laptop in and then set the IP configuration including /etc/resolv.conf and write proxy settings in /etc/proxy. A perl script to edit your netscape 4 preferences is included. You can also run a custom script for each network to edit /etc/printcap or /etc/issue or whatever you feel like. The ARP method is much quicker than the "ping" method that other solutions use.
eCos (Embedded Configurable OS) is an open source, configurable, portable, and royalty-free embedded Real Time Operating System. It is written in C++, provides all the usual OS things. You configure the OS so that the parts you don't need aren't loaded to the embedded system. eCos is released under a modified GPL that allows for its use in embedded systems without having to GPL the embedded application.