The Heirloom Toolchest is a collection of standard Unix utilities. It was derived from original Unix material released as open source by Caldera and Sun, and contains multiple versions of each utility corresponding to SVID3/SVR4, SVID4/SVR4.2MP, POSIX.2-1992/SUSV2, POSIX.1-2001/SUSV3, and 4BSD (SVR4 /usr/ucb). It processes lines of arbitrary length and in many cases binary input data, supports characters in UTF-8 and many East Asian encodings, and contains more than 100 individual utilities including bc, cpio, diff, ed, file, find, grep, man, nawk, oawk, pax, ps, sed, sort, spell, and tar. Extensive documentation is included.
ECB is a source code browser for (x)emacs. It displays a couple of windows that can be used to browse directories, files, and file contents like methods and variables. It supports source code parsing for languages like Java, C, C++, Elisp, Scheme, Perl, TeX, LaTeX, etc. In addition, it offers an (optional) permanent "compile window" at the bottom of the emacs frame, which is used to display all help and compile output. The rest of the frame is called the "edit area", which can be divided into several edit windows that are used for editing the sources. Deleting some of the edit windows neither destroys the compile window nor the browsing windows. It requires the CEDET suite.
Wocvim is a WoC client for Vim. WoC is a protocol which enables the use of hyperlinks in plain ASCII texts. The links can point to local or remote locations. The protocol is specifically designed to support source code, but it can be used in any text. For source code, it's also possible to use ad-hoc tag generators like cscope and ctags.