KDE 3.1 comes with a new kioslave called "fish". This implements a file transfer protocol over ssh and scp. Because it's a kioslave, it can be used pretty much anywhere that KDE programs interact with "filesystems".
The most obvious application is Konqueror, where I can type "fish://richard@machine" into the URL bar and I then browse files and directories at the remote machine, all over ssh/scp. The kioslaves are also used in things like the KDE file dialog. When I'm at work, I can choose to load or save files to my home machine by simply entering a fish:// path. I don't need to type that in any more, because of course the KDE file dialog also includes bookmarks.
See also my previous entry about the audiocd kioslave. Note that back then I didn't make the connection about them being useful in all KDE-aware apps. That means that I could, if I was so inclined, compose an email to Rachel and attach an ogg-vorbis music track from a CD I'd just bought - which would rip it then and there - so she could hear it before I got home in the evening. That's pretty goddamn neat :)