Open-source software is software that is intended to have it’s code freely exposed to the public. This means that a program can be contributed to by any number of people that wish to help to improve it. While open-source projects have existed for many years, often beginning as a mere hobby for one person, awareness and interest has exploded recently. There are now alternative open-source software programs for just about every major commercial application making the transition away from Windows or Apple is a lot easier than most people think.. While some free programs may not feature all the bells and whistles or appear quite as polished as their payed for brethren, they generally get the job done satisfactorily. In some cases, a privately developed, free or cheap application may even be “better” than the commercial version running faster and more efficiently.
Open-source software exists on every computer operating system. It’s actually rare to find a Linux only application as generally they’ll be created for Windows and Linux, Apple OS and Linux, or all three. This gives you a good opportunity to test out software on your current OS before making the leap to Linux.
The goal of this article is to build an everyday computer using completely free software. Starting with the basics that just about every computer shouldn’t go without. Follow up articles will focus on graphic and web design as well home theater.
If you plan on leaving Windows or OS X behind, you’re going to need a Linux operating system. Ubuntu is perhaps the most popular for non-commercial users. It features an extremely refined interface that is intuitive and easy to use and it comes with many applications built right in (like OpenOffice, Evolution Mail, Firefox, music and movie players, view and edit photos) so you can begin using a Linux based computer instantly, without having to spend lots of time installing other software. Best of all, Ubuntu lets you test drive the OS from a CD or USB drive without ever installing it on your hard drive. It’ll be a little slow and won’t let you save settings or preferences but it’s a great way to get your feet wet. You can also run Ubuntu (along with other Linux distros) side-by-side Windows which gives you a chance to not only experience the OS but also test for any hardware and driver problems you may encounter before making the switch.
If Ubuntu isn’t quite what your looking for, there’s a plethora of other distributions, both major and minor that are worth looking into. DistroWatch keeps tabs on all the different versions of Linux that are available along with descriptions of each and even provides copies of the OS on disc and flash drives for a small fee.
Spreadsheets and Word Processing
OpenOffice.org and Google Docs
Windows, OS X, Linux
For many people, Â replacing Microsoft Office is the first hurdle to overcome when moving to open-source platforms. Luckily there’s two excellent programs available that fulfill that role and are even compatible with Office. Both applications can be used in place of Word, Excel, and PowerPoint. OpenOffice also includes a simple drawing program similar to Visio. If you prefer to work in the cloud and store your documents online so that they can be accessible wherever you have an internet connection, Google Docs is a simple solution that offers powerful features not normally associated with a mere website.
Email
Thunderbird and Evolution
Windows, OS X, Linux (Evolution is Linux only)
If you prefer to use an application for your email client rather than going to a website then you’ll likely need a program to replace Outlook or Mail. While Thunderbird may be more widely available, Evolution comes preinstalled on Ubuntu. Both offer junk mail filtering and integrated calendars to keep track of appointments and invites. Thunderbird also incorporates a migration assistant to help those moving over from Outlook as well as Firefox like Add-ons to further customize your experience.
Instant Messaging
Pidgin
Windows, OS X, Linux
Pidgin consolidates all your IM services into one client, allowing you to chat simultaneously with multiple people over multiple services, all from one program.
Adium
OS X
While Adium is Mac only, I’m including it here because it is the defacto standard for IM clients on the Mac. While iChat supports video it only allows you to access MobileMe (.Mac), Google Talk (Jabber) and AIM accounts. Â With Adium, you lose video, but gain everything else.
File Compression
7-Zip
Windows, Linux
7-Zip is essential a free version of WinZip and WinRAR. It does all of the above, is free so you don’t get those annoying trial warnings every time you accidentally fully open the program  and it offers its own compression format which it claims is more efficient.
Stuffit Expander
Windows, OS X
There is no Linux version available here, but like WinZip for Windows, Stuffit has long been Mac’s goto file archiving program. Its basic expander version is free and now has a Windows version as well. Simply included as another free alternative.
Security
AVG Anti-Virus
Windows, Linux
This is your free alternative to spending money on Norton to protect yourself from all those porn sites and suspicious emails. While it’ll satisfy Window’s lust for reminding you about security, if you want complete protection you may want to opt for the paid version scan downloads and your hard drives.
Web Browsing
Firefox, Chrome, Opera, Safari
Windows, OS X, Linux
Since the popularity of  Firefox most people are aware that there are other browsers besides Internet Explorer. But why should you use a browser other than what came with your computer? Speed, security and proper page display. Explorer is notorious for lacking in all. Chrome and Safari especially trump Explorer when it comes to displaying web pages quickly and both start up faster when opening. Firefox offers thousands of Add-ons to customize the browser to your heart’s content while Opera is fast, simple and extremely innovative. All have much better security measures to ensure you don’t inadvertently contract a virus while surfing and all have much better support for web design standards meaning pages look how they’re supposed to.
Music & Video
Ubuntu comes with Rhythmbox (for music), Movie Player, Pitivi video editor, and F-Spot (for organizing and editing photos) but here are some additional alternatives
VLC Media Player
Windows, OS X, Linux
Pretty much any media nerd knows that VLC is the defacto standard for simple, jack-of-all-trades media players. VLC is just about as bare bones as you can get… but it supports just about everything. Nearly any video or audio format, subtitles, chapters, stereo or surround sound, multiple languages, playlists, etc. About the only thing it doesn’t do is maintain a visual library of your collection.
Boxee
Windows, OS X, Linux, Apple TV
For the home entertainment experience, Boxee makes it possible. It scours your hard drives for media, identifies it and then presents it in an organized fashion letting you enjoy everything from music to movies to TV to internet feeds like YouTube and Netflix. However, Boxee is without it’s disadvantages: it’s a full screen only application – which is fine for watching movies or TV. Maybe not so good when you want to listen to music while surfing the internet or playing games. It also won’t let you edit metadata since it identifies media itself and displays information based on what it gathered from internet sources. Because of this, improperly named files won’t be identified and will be ignored. However, this also makes it easy to intentionally ignore certain files. Properly, configured, Boxee is ideal for dedicated Home Theater PCs.
Amarok
Linux
If  Rhythmbox doesn’t quite do it for you, Amarok will. With support for a wide variety of audio formats it has powerful features for integrating devices and services and an intuitive interface.
Torrent File Sharing
Transmission
OS X, Linux
Transmission is super light-weight and easy to use. Even behind a firewall it’ll automatically search for an open port. If none can be found, you can edit the port settings yourself. There’s really nothing fancy about it. Simply download and upload torrents with ease. Although it does have a nice little ‘ding’ sound when a torrent is complete.
Emulation/Virtual Machine
Wine
Linux
Wine isn’t exactly an emulator or a VM. It simply allows you to run many Windows applications on a Linux OS. It’s not perfect and not every program is supported. However, many common programs are supported and if you’re determined to ditch Windows, Wine may help you make the jump even if some of your essential programs haven’t yet.
You can also find these applications and many others at Free Applications.