PeaZip is a cross-platform file archiver utility that provides a unified portable GUI for many open source technologies like 7-Zip, FreeArc, PAQ, UPX, etc. Creates 7Z, ARC, BZ2, GZ, *PAQ, PEA, QUAD/BALZ, TAR, UPX, WIM, XZ, and ZIP files. It extracts more than 150 archive types: ACE, ARJ, CAB, DMG, ISO, LHA, RAR, UDF, ZIPX, and more. Features of PeaZip include extracting, creating, and converting multiple archives at once, creating self-extracting archives, split/join files, strong encryption with two factor authentication, an encrypted password manager, secure deletion, find duplicate files, calculate hashes, and export job definitions as scripts.
Spack is a standalone package manager with its own CPIO-based package format but aiming to keep total compatibility with Slackware Linux. Written in POSIX shell as much as it makes sense, it attempts to provide a fairly complete toolkit to build, install, remove, list, retrieve, and arrange your packages. It can be used as an alternative to Slackware's pkgtools, just to independently and properly manage your local software on any distribution, or as the main package manager of the distribution you build yourself.
Dar is a shell command that makes backup of a directory tree and files. Its features include splitting archives over several files, DVD, CD, ZIP, or floppies, compression, full or differential backups, strong encryption, proper saving and restoration of hard links, extended attributes, file forks, Door inodes, and sparse files, remote backup using pipes and external commands (such as ssh), and rearrangement of the "slices" of an existing archive. It can run commands between slices, before and after saving some defined files or directories (for a proper database backup, for example), and quickly retrieve individual files from differential and full backups. Several external GUIs exist as alternatives to its CLI interface, like kdar, DarGUI, SaraB, etc.
slapt-get is an APT-like system for Slackware package management. It allows you to search Slackware mirrors and third-party package sources (such as www.linuxpackages.net) for packages, compare them with installed packages, and install new packages or upgrade installed packages, all with a few simple commands.
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.
slkbuild is a script inspired by makepkg from Arch that greatly simplifies the package building process in Slackware and derivatives. It parses an easy-to-create SLKBUILD meta-file and from that creates a conventional build script that follows all of the Slackware packaging standards and that can be run on its own. The advantage of using slkbuild is that it ensures package uniformity and allows for an easy-to-edit meta-file in the event that one might require customization or might need to update the script for new releases. It also makes the build process much quicker, since it takes care of downloading the source, untarring, gzipping man and info pages, stripping binaries, making sure that the menu entry for a graphical application is compliant, as well as a host of other things.