Open source applications have a natural inclination to be compiled for multiple operating systems. Although many OS’s and tools are converging in functionality, it’s nice to have a homogeneous environment of favorite programs to make the transition from machine to machine more seamless. I use Windows and work and Linux at home, but that doesn’t mean I have to give up anything in the process. Below are – in no particular order – some of my favorite cross-platform open source applications.

The List

Deluge

Deluge is a bittorrent client similar to the now-official µTorrent in Windows. While this particular program is not alone in this space, I find the interface of Transmission far too simple for my preference. Fortunately, we have choice! Deluge supports popular features such as encryption and web interface. Extensibility is built-in with support for plugins, including an eMule-style IP block list.

Deluge Screenshot

FileZilla

I discovered this application years ago when it was Windows-only. Since then, the author has completely rewritten it from the ground up using wxWidgets and a variety of other open source tools. FileZilla is an absolutely amazing FTP client that also supports FTPS and FTP along with a bevy of helpful features such as bookmarks, filename filters and proxy support. This utility is one that I install everywhere.

FileZilla Screenshot

Firefox

Probably the most well-known open source application, Firefox’s usage share has steadily climbed since pre-1.0 days. It is the second most popular browser after only Internet Explorer and has widely spread on other OS’s where IE is not a choice. The plugin and theme architecture mean that the browser can serve many needs – such as website debugging and even IRC – that once required multiple utilities.

Firefox Screenshot

hellanzb

Continuing the network theme, we have probably my most favorite application, hellanzb. This is a usenet binary downloading program at its finest. Give it an NZB and it takes care of the rest, including download, parchive check, and extraction. If you use Usenet for downloads, go get this right now. It is officially supported on any Unix-like OS, including OS X. An automated installer and Cygwin guide are available for Windows users. Be forewarned, hellanzb is a command-line tool, which works great in it’s own right. Fortunately, it provides an XML RPC interface allowing GUI applications to be easily built on top of it. Below is a screenshot of one of those tools: Remote HellaNZB GUI. If you’re looking for a UI that is cross-platform as well, tools built on platforms like Adobe AIR will fit-the-bill.

Remote HellaNZB GUI Screenshot

Pidgin

Originally known as Gaim, Pidgin is probably the most-used multi-service IM application across all operating systems. Even though OS X users love Adium, it’s the libpurple engine underneath Pidgin that drives it all. This is another program that supports theme and plugins, increasing its usefulness. I would suggest you try it out, but if you’re reading this, there’s a good chance you already have.

Pidgin Screenshot

KeePassX

KeePassX started as a port of KeePass for Windows known as KeePass/L. When the application finally became cross-platform, KeePass/L was changed to its KeePassX. Although it can only read and save KeePass 1.x-style databases, this utility is becoming indispensable in a world of dozens of passwords. The database is stored in your choice of encryption (AES or Twofish) with one or both of password and key file. In addition to simply storing login information, KeePassX can also generate passwords based on your own filters and help automate the filling-in of login forms.

KeePassX Screenshot

TrueCrypt

TrueCrypt is another piece of desktop encryption software. It allows users to create self-contained encrypted volumes or entire encrypted partitions. This utility also supports multiple encryption algorithms and forms of authentication. In addition to the end-user tools like a Quick-start guide, the author has posted a very detailed explanation of the internal mechanisms. Geeks rejoice!

TrueCrypt Screenshot

VirtualBox

My love for VirtualBox is no secret. What I truly love about VirtualBox is that the underlying virtual disk images are OS-agnostic, I can easily move a VDI from Linux to Windows to Mac, and the guest operating system doesn’t care. Furthermore, with the added ability to read VHD and VMDK formats, this has become my virtualization software of choice.

Virtualbox Screenshot

Handbrake

Handbrake is an absolutely amazing video transcoding application. Give it just about any file format and convert it to many destination formats on-the-fly. Recently downloaded a FLV off YouTube and want to keep a local copy on your iPhone? Just a few clicks and Handbrake can help with that. Supports a queue for batch operation and works efficiently.

Handbrake Screenshot

VLC

The great thing about VLC is that it can play just about as many formats as Handbrake can convert. All the A/V support is built-in, so there’s no need to worry about gathering the necessary codecs. It can often stand on its own, but also works great as a supplemental video player.

VLC Screenshot