Simple Package Manager (SPM) is intended to operate in a way similar to existing package managers (apt, dpkg, Pacman, etc.). Instead of supporting a centralized package repository, SPM allows remote packages to be downloaded and installed automatically, given their URL. This allows a developer to package and distribute software via a package management system without having to worry about the many different formats and Linux distribution repositories.
Showkeys is a simple program to display keys being pressed on the screen. It is useful while making presentations and screencasts. The audience will be able to see the keys being pressed. It is similar to key-mon. Key-mon has more features than showkeys. but the latter solves some specific problems: it doesn't use GTK/GNOME; uses libxosd to display keys directly onto the screen; has no floating windows to that always need to be on top (which is very useful if you're using a tiling WM like Xmonad); and has keystroke history. key-mon has keystroke history, but doesn't show modifiers. showkeys does, using an Emacs style key notation.
getxbook is a collection of tools to download books from websites. There are tools to download from Google Books' "book preview", Amazon's "look inside the book", and Barnes and Noble's "book viewer". There is an optional GUI written in Tcl/Tk, and some shell scripts using OCR to create plain text or searchable PDFs and DjVu files from the downloaded books.
PFFFT is a very small 1D Fast Fourier Transform library based on the venerable FFTPACK v4. It handles single precision real and complex transforms. Computations take advantage of SSE1 instructions on x86, Altivec on PowerPC, and NEON on ARM, allowing it to achieve a performance level that is not too far from the very best FFTs (FFTW, Intel MKL, Apple vDSP).