NetBSD is a free, highly portable UNIX-like operating system available for many platforms, from 64bit alpha servers to handheld devices. Its clean design and advanced features make it excellent in both production and research environments, and it is user-supported with complete source. Many applications are easily available.
The first version of NetBSD (0.8) dates back to 1993 and springs from the 4.3BSD Lite operating system, a version of Unix developed at the University of California, Berkeley (BSD = Berkeley Software Distribution), and from the 386BSD system, the first BSD port to the Intel 386 CPU. In the following years, the modifications from the 4.4BSD Lite release (the last release of the Berkeley group) have been integrated in the system. The BSD branch of Unix has had a great importance and influence in the history of this operating system, to which it has contributed many tools, ideas and improvements (the vi editor, the C shell, job control, the Berkeley fast file system, reliable signals, support for virtual memory, TCP/IP implementation, just to name a few) which are now standard in all Unix environments. This tradition of research and development survives today in the BSD systems (free and commercial) and, in particular, in NetBSD.
NetBSD operates on a vast range of hardware platforms and is very portable, probably the most portable operating system in the world. The full source to the NetBSD kernel and userland is available for all the supported platfoms; please see the details on the official site of the NetBSD Project.
A detailed list of NetBSD features can be found at the following URL http://www.netbsd.org/Misc/features.html.
The basic features of NetBSD are:
Portability (more than 20 platforms are supported)
Code quality and correctness
Adherence to the standards
Research and innovation
The aforementioned characteristics bring also indirect advantages. For example, if you work on just one platform you could think that you're not interested in portability. But portability is tied to code quality: without a well written and well organized code base it would be impossible to support that many platforms. And code quality is the base of any good and solid software systems, though surprisingly few people seem to understand it. The attention to architectural and quality issues is rewarded with the great potentiality of NetBSD's code and the quality of it's drivers.
One of the distinguishing characteristics of NetBSD is not to be satisfied with partial implementations. Some systems seem to have the philosophy of "If it works, it's right". In that light NetBSD could be described as "It doesn't work unless it's right". Think about how many overgrown programs are nowadays sadly collapsing under their own weight and "features" and you'll understand why NetBSD wants to avoid this situation at all costs.
NetBSD 1.4.1 supports the following platforms (you can find the technical details for all of them on the NetBSD site)
Digital Alpha (64bit)
Commodore Amiga, MacroSystem DraCo
Acorn RiscPC/A7000, CATS, Digital Shark, EBSA-285, VLSI RC7500
Atari TT030, Falcon, Hades
Hewlett-Packard 9000/300 and 400
i386 family IBM PCs and clones
Apple Macintosh
Apple Power Macintosh
Motorola MVME 68k SBCs
NeXT 68k 'black' hardware
The PC532
Digital MIPS-based DECstations and DECsystems
Sun SPARC
Sun 3 and Sun3x
Digital VAX
Sharp X680x0
The NetBSD site states that: "The NetBSD Project provides a freely available and redistributable system that professionals, hobbyists, and researchers can use in whatever manner they wish". I would add that NetBSD is an ideal system if you want to learn Unix, mainly because of its adherence to standards (one of the project goals) and because it can run on hardware which is considered obsolete by most other operating systems; we could say "to learn and use Unix you don't need to buy expensive hardware: you can reuse the old PC or Mac that you have in your attic". Also, if you need a Unix system which runs consitently on a variety of platforms, NetBSD is probably your best (only) choice.
When you install NetBSD you have a rich set of programs and applications that you can install on your system. Besides having all the standard Unix productivity tools, editors, formatters, C/C++ compilers and debuggers and so on, there is a huge (and constantly growing, I think it is now over 1000) number of packages that can be installed both from source and in pre-compiled form. All the packages that you expect to find on a well configured system are available for NetBSD for free and there is also a number of commercial applications. You can also make use of one of the available emulation to run binaries from other *nix operating systems. Linux emulation is probably the most relevant example, lots of efforts have gone into it and it is used by almost all NetBSD users; you can run the Linux version of
Netscape
Acrobat Reader
Doom, Quake
Adobe FrameMaker
many other programs
NetBSD is also capable of emulating FreeBSD, BSDI and other systems.
Differently from many contemporary operating systems, the NetBSD installation, though feature rich is not huge in size, because it strives to produce a stable and complete base system without being redundant. After the installation you get a fully working system which still lacks a number of applications like, for example, a web browser (NetBSD, contrary to other OS, does not consider the browser as part of the base system): you have the freedom to decide which programs to install on your machine and the installation of new programs is very easy with the packages collection.
Another advantage of this approach is that the base system will work without these additional packages; if you decide to upgrade your version of Perl you need'nt be afraid to break some parts of your system. When you install NetBSD you don't find huge pre-packaged collections of applications: you may now see this as a disadvantage but when you start understanding the philosophy behind this you will find that it gives you freedom. When you install these software collections (which someone else has decided for you) you fill your hard disk with tons of programs, most of which will stay unused (and unknown) and only waste space (and possibly make the system less stable): this is something which the typical BSD user doesn't want to do.
Even when you start knowing NetBSD, there is always something that will continue to amaze you, the extreme consistency and logic of the system and the attention to the details: nothing appears the result of chance and everything is well thought out. Yes, that's what quality is about and, in my opinion, this is the most distinguishing feature of NetBSD.
We could spend days arguing on the relative merits of operating systems (and some people like to do it) but if you don't try something seriously you can't really judge. I am convinced, because I saw it many times in the mailing lists, that if you try NetBSD you'll be conquered by the perfect balance between complexity and effectiveness; all problems have more than one solution: NetBSD is not happy with "a" solution but always tries to find the easiest and most elegant one. NetBSD is a tool that enables you to do your work without getting in your way. In this light it is an optimal tool; it's like using a pen: you work hard to learn how to use it but once you've learned you can write or draw and completely forget about the pen.
There is no "official" supplier of NetBSD CD-ROMs but there are various resellers. You can find the most up to date list on the relevant page on the NetBSD site. Of course you can also download NetBSD from the Internet from one of the mirrors.