1. FreeBSD Inc. FreeBSD is an advanced BSD UNIX operating system for "PC-compatible" computers, developed and maintained by a large team of individuals.
2. Linux Linux is a free Unix-type operating system originally created by Linus Torvalds with the assistance of developers around the world. Linux is an independent POSIX implementation and includes true multitasking, virtual memory, shared libraries, demand loading, proper memory management, TCP/IP networking, and other features consistent with Unix-type systems.
3. Debian Debian is a free, or Open Source, operating system (OS) for your computer. An operating system is the set of basic programs and utilities that make your computer run. At the core of an operating system is the kernel. The kernel is the most fundamental program on the computer, does all the basic housekeeping and lets you start other programs. Debian is kernel independent. It currently uses the Linux kernel but work is in progress to provide Debian for other kernels, using the Hurd.
4. Linux/Kernel Archives This is the primary site for the Linux kernel source, but it has much more than just kernels - there is a 20 GB of disk space set aside for mirroring the largest Linux-related software archives.
