Some underdogs that more people should know about.
toast: Automated software retrieval, compilation, installation, and removal with safe compartmentalization and non-root usage. Works without hassle 90% of the time. Supports a variety of package types, including autotools, plain prefix-dir, plain make, distutils, Cabal, and more.
pandoc: Markdown done right. A sane markup (structured text) language supporting a variety of input and output formats, including HTML, man, and TeX. AsciiDoc is a close runner-up; ReST is more complex. Pandoc includes support for both of these. Hopefully the future will yield markup languages with greater extensibility and enough flexibility to be used in everything from wikis to comment documentation.
rubber: A usable frontend for LaTeX and all its friends: BibTeX, image converters, etc. Similar to but more modular than latexmk.
Emacs has make-frame-on-display, but it’s quirky (e.g. going to the minibuffer locks up everything else). Vim also has a “collaborative editing” as an item sponsors can vote on. screen can be a poor man’s collaborative editor (it’s decent as a whiteboard, at least).
Opera: The fastest, smallest browser I’ve used is also the most usable and comes with the most features out of the box. Its M2 mail client is awesome too, but alas, it’s too buggy. KHTML is probably the closest-performing engine, but I’ve found it to be too crash-prone.
gprof2dot: A handy tool for visualizing the callgraph results of gprof, the Google CPU profiler, python cProfile, and more.
wtf: A filter for g++’s obscure page-long template errors. Resulting error messages are readable and beautified. See also gstlfilt.