KIO slaves are some of the most useful features of the KDE desktop, but many users aren't aware they exist. You probably use some of them know without even realizing it. A kioslave is a protocol that provides support for individual protocols that may provide access to files, web sites, and more. Below I will outline some of the most popular and most interesting kioslaves.
This listing is far from complete. The full list of KIO slaves installed on your system can be found by running KInfoCenter and checking the Protocols section.
Files and Web Sites
Two of the most commonly used kioslaves are file and http. file is used by all KDE applications to display locally available files. Entering file:/home/~ in Konqueror would list everything available in your home directory. http and its sibling https are used to display web sites. It is this protocol that allows Konqueror to be a web browser.
Most major compression protocols have a kioslave included with KDE. ar, bzip, bzip2, gzip, tar, and zip are the ones currently installed on my system. The benefit of this is that any KDE program can easily browse the files within an archive. To access a tar archive, simply enter tar:/ followed by the path to the document. Clicking on a tar file in Konqueror will automatically open it using the tar kioslave.
When I first started using Linux one of the first apps I looked for was a good FTP client. It wasn't until later that I discovered I had one all along and didn't even know it. Konqueror has now become my FTP client of choice. I can easily keep bookmarks of my sites and access each of them just like it was part of my local file system. And if you need more security, sftp has its own kioslave that will send your files over an encrypted ssh transport. If you need advanced features, then a more fully featured FTP client is definitely worth looking into.
If you have a home network then this section is definitely of interest. Many of us need to access files that are stored on other computers and set up shared drives to do it. Samba (compatible with Windows file sharing) and NFS are the most heavily used protocols for the home user. While it is possible to use a stand-alone share browser, it is much easier to simply access your files directly using the smb and nfs kioslaves.
Another option is called remote. The remote:/ kioslave opens up a link to browser your Samba Shares or to add your own network folder. Selecting the Samba Shares link opens up the smb:/ kioslave that goes out and finds every available computer in you workgroup. From there it's a simple matter of selecting the computer and folders you want just as if you were browsing locally. If you used NFS instead of Samba, the nfs:/ path will get you right where you need to be.
One of the coolest kioslaves is called audiocd. After inserting a CD into your drive, open Konqueror and type in audiocd:/. It will display a list of the discs tracks along with some folders. Which folders depends upon the audio codecs you have installed. On my computer there are folders called OGG, FLAC, and MP3. Open any one of them and you will again see a list of the CD's tracks, but this time with a file extension matching the folder name. Drag and drop the tracks to a folder in your home directory and they will automatically get transcoded as they copy. CD ripping has never been easier.
Do you own and iPod? If so, iPod Slave is just what you have been looking for. Installing it will allow you to organize playlists and upload tracks with ease. Point either Konqueror or amaroK to ipod:/ and they will display the Artists, Playlists, and Utilities directories. More dragging and dropping and you can transfer any files you want.
iPod not your thing? How about a PlayStation Portable (PSP)? The KPSP will let you type psp:/ into Konqueror to browse and control your media.
Still not satisfied, install the Creative Nomad JukeBox KIO Slave and access it just like the other two, this time using njb:/.
Moving in a slightly different direction we have SynCE-KDE. It will allow you to browse the file system of a Windows CE device. An applet also comes with this program to allow easy access and synchronization.
Windows using Wine
The final kioslave I will mention is called K-Wine. Installing Windows apps on Linux using Wine is great if you have those few situations where you haven't yet converted to a native Linux app, but the virtual file system that is used can sometimes be frustrating. K-Wine solves that problem. It adds a new menu section called Wine to Konqueror's left sidebar. Selecting it will show a listing of the Wine accessible drives using their Windows drive letters. No all of you files are once again right at your finger tips.
Thanks for reading this KIO slave round-up. Please post comments about other cool kioslaves that may have missed.