Nix is a purely functional package manager. It allows multiple versions of a package to be installed side-by-side, ensures that dependency specifications are complete, supports atomic upgrades and rollbacks, allows non-root users to install software, and has many other features. It is the basis of the NixOS Linux distribution, but it can be used equally well under other Unix systems.
smake is a highly portable 'make' program that makes commands up to date based on rules in Makefiles and on the timestamps of the related files. It implements a complete superset of the features of the classical POSIX/Unix make program. It warns about typical misuse of dynamic macros that prevent portability of makefiles. Its automake features allow you to run scripts to automatically create rules for unknown platforms.
BitRock InstallBuilder allows you to create easy-to-use multiplatform installers for Linux (x86/PPC/s390/x86_64/Itanium), Windows, Mac OS X, FreeBSD, OpenBSD, Solaris (x86/Sparc), IRIX, AIX, and HP-UX applications. The generated application installers have a native look-and-feel and no external dependencies, and can be run in GUI, text, and unattended modes. In addition to self-contained installers, the installation tool is also able to generate standalone RPM packages.
stowES (stow Enhancement Script) is a Perl script which tries to ease the use of the "stow" packaging program and software which can be compiled and installed with autoconf. It automates the compilation and installation of software packages and provides some useful functions to maintain your stow packages (e.g., list packages, check packages for integrity, etc.).
The main goal of autopkg.pl is to build software and make a Slackware package without having to make a build script of some kind. A single config file can specify the compile-time options for every program compiled with autopkg.pl. The packages are created in their own build directories and never installed unless you want them installed. A setuid-root wrapper allows normal users to create packages (with proper user/group listings and permissions) and optionally install them depending upon a list of trusted users. Optional "hint files" can also help a broken or not-that-well-set-up package to be compiled and packaged properly (samples included).