Invoking \"Download Media\" by right clicking a podcast item in the playlist section causes it to be downloaded into a file in $HOME/.kde/share/apps/amarok/podcasts/data . What then? Should I move it into a directory in my sound archive ($HOME/mp3) or is there some way that amaroK is made aware of it automatically, so as to add it to the Collection? Or whatever?

After downloading, just right-click on the same podcast entry, and then click Play. That simple