GParted
The UNIX philosophy is based on tools that "do one thing and do it right", and GParted is a perfect example. Partition management under Linux involves a raft of different tools - not just the partition editors themselves, but also the separate formatting and resizing utilites for each filesystem. GParted gives you a single GUI interface that lets you create, delete, resize, and format partitions of all types with ease. It's also downloadable as a live CD.
Handbrake
We mentioned Handbrake in our feature of the Web's Best 50 Free Downloads. A number of DVD rippers and video conversion tools exist for Linux, but most of them are command-line based with obscure interfaces. Handbrake, though, is entirely GUI-based, letting you rip and convert videos with ease. The GUI gives you access to a full range of options, but for easy use it has preset conversion profiles for specific devices, such as iPods and the PSP. It also has a batch mode, so you can queue multiple conversion jobs and run them all automatically. Also available for Windows and Mac OS X.
rsync
If you need to copy files between PCs on a regular basis, you need to know about rsync. It's a command-line tool that can copy entire directory structures in a single operation. And if you're overwriting an existing copy, it will only copy the files that have changed, so it's perfect for backups or synchronising servers. It can even compare individual files on the two systems and copy just the differences - very handy for fixing corrupt Linux ISO downloads. Also available for Windows and Mac OS X.
XBMC
Formerly the Xbox Media Center, XBMC has expanded beyond the original Xbox to flex its media-playing muscle on other platforms. Like MythTV, XBMC offers a large, streamlined UI that's perfect for use on a TV, and while it lacks MythTV's PVR-style digital TV features, it's easier to install and more slick to use than MythTV if you just want to watch ripped or downloaded videos. It also has plugins to stream trailers and Youtube videos. Also available for Windows, Mac OS X and Xbox.
ClamAV
You might be surprised to find a virus scanner in this list, but don't worry - it's not for Linux viruses! ClamAV scans for Windows viruses, but that's more handy on a Linux box than you might think. ClamAV on a live CD or separate partition can scan your Windows drive without ever having to run Windows. It can run scheduled scans across your file servers, and on a mail server, it can protect an entire network from email viruses. Also available for Mac OS X.
Got a favourite Linux app? Add your suggestion in the comment box below.
Also see: 5 More Free PC Apps You Can't Do Without (Part 2)
Also see: 5 Free Linux Apps You Can't Do Without (Part 1)
Also see: 5 More Free PC Apps You Can't Do Without (Part 2)
Also see: 5 Free PC Apps You Can't Do Without (Part 1)
Also see: My life with Linux: the daily ups and downs of switching to open source