Linux Kernel v3.0 is here! The main changes, from kernelnewbies.org: Besides a new version numbering scheme, Linux 3.0 also has several new features: Btrfs data scrubbing and automatic defragmentation, XEN Dom0 support, unprivileged ICMP_ECHO, wake on WLAN, Berkeley Packet Filter JIT filtering, a memcached-like system for the page cache, a sendmmsg() syscall that batches sendmsg() calls and setns(), a syscall that allows better handling of light virtualization systems such as containers. New hardware support has been added: for example, Microsoft Kinect, AMD Llano Fusion APUs, Intel iwlwifi 105 and 135, Intel C600 serial-attached-scsi controller, Ralink RT5370 USB, several realtek rtl81xx devices or the Apple iSight webcam. Many other drivers and small improvements have been added.

Linux is a clone of the operating system Unix, written from scratch by Linus Torvalds with assistance from a loosely-knit team of hackers across the Net. It aims towards POSIX and Single UNIX Specification compliance.

It has all the features you would expect in a modern fully-fledged Unix, including true multitasking, virtual memory, shared libraries, demand loading, shared copy-on-write executables, proper memory management, and multistack networking including IPv4 and IPv6.

Although originally developed first for 32-bit x86-based PCs (386 or higher), today Linux also runs on (at least) the Alpha AXP, Sun SPARC, Motorola 68000, PowerPC, ARM, Hitachi SuperH, IBM S/390, MIPS, HP PA-RISC, Intel IA-64, AMD x86-64, AXIS CRIS, Renesas M32R, Atmel AVR32, Renesas H8/300, NEC V850, Tensilica Xtensa, and Analog Devices Blackfin architectures; for many of these architectures in both 32- and 64-bit variants.

Linux is easily portable to most general-purpose 32- or 64-bit architectures as long as they have a paged memory management unit (PMMU) and a port of the GNU C compiler (gcc) (part of The GNU Compiler Collection, GCC). Linux has also been ported to a number of architectures without a PMMU, although functionality is then obviously somewhat limited. See the µClinux project for more info.