John the Ripper is a fast password cracker, currently available for many flavors of Unix, Windows, DOS, BeOS, and OpenVMS. Its primary purpose is to detect weak Unix passwords. It supports several crypt(3) password hash types commonly found on Unix systems, as well as Windows LM hashes. On top of this, lots of other hashes and ciphers are added in the community-enhanced version (-jumbo), and some are added in John the Ripper Pro.
Owl (Openwall GNU/*/Linux) is a small security-enhanced Linux distribution for servers. Owl also makes a good base system for customized virtual machine images and embedded systems, and Owl live CDs with remote SSH access are good for recovering or installing systems (whether with Owl or not). A single Owl CD includes the full live system, installable packages, the installer program, as well as full source code and the build environment capable of rebuilding the entire system from source. Owl supports multiple architectures (x86, x86-64, SPARC, and Alpha) and offers some compatibility for packages developed for other Linux distributions. The primary approaches to security are proactive source code review, privilege reduction, privilege separation, careful selection of third-party software, safe defaults, and "hardening" to reduce the likelihood of successful exploitation of security flaws.
Partition Logic is a partitioning and disk management tool for PC-compatible computers. It includes its own standalone operating system and GUI, and can fit on a single bootable floppy (or CD). It creates, modifies, resizes, deletes, formats, and moves partitions, and copies hard disks. It is based on the Visopsys operating system.
crypt_blowfish is an efficient implementation of a modern password hashing algorithm, based on the Blowfish block cipher, provided via the crypt(3) and a reentrant interface. It is compatible with bcrypt as used in OpenBSD. It is adaptable to future processor performance improvements, allowing you to arbitrarily increase the processing cost of checking a password while still maintaining compatibility with your older password hashes. The hashes it produces are several orders of magnitude stronger than traditional Unix DES-based or FreeBSD-style MD5-based hashes.
The Openwall Linux kernel patch is a collection of security "hardening" features for the Linux kernel. In addition to the new features, some versions of the patch contain various security fixes. The "hardening" features of the patch, while not a complete method of protection, provide an extra layer of security against the easier ways to exploit certain classes of vulnerabilities and/or reduce the impact of those vulnerabilities. The patch can also add a little bit more privacy to the system by restricting access to parts of /proc so that users may not see what others are doing.
Powertweak-Linux is a tool to tune your system to its optimal performance settings. It started life as the replacement for the now obsolete kernel option 'tune PCI bridges', and has been extended to provide more features and support more chipsets. It can also tune network/filesystem performance using /proc/sys entries, disk elevator settings, and x86 CPU registers (needs 2.2.18 or 2.4.0test kernel), CDROM speeds, hdparm type features, and Sony VAIO backlight. It has both a GTK GUI and a text-based lister.