Downloading videos from YouTube isn't a problem thanks to tools like clive. But fetching all videos of a playlist was always a little bit tricky. There is clivescan, but it requires user intervention and needs Tk. Other tools have focused on feed parsing, so in case you have a playlist feed you can then download all (listed) videos. But none of the tools offered me a simple way to download all videos in a playlist from the command line. That's when I started writing ytplaylistfetcher, a simple shell script aiming to parse a YouTube playlist, extract all unique video ids and pass the list on to clive for downloading.
By now ytplaylistfetcher is pretty much complete and there aren't many changes ahead (unless YouTube changes its page layout again, e.g. back to multi-page playlists).
At the moment ytplaylistfetcher can handle the three common playlist link formats. If you've encountered another format or found a playlist link that doesn't work, let me know.
ytplaylistfetcher has just one limitation in my opionin (but one I can live well with): it is limited to YouTube playlists. But that isn't a severe drawback in my opinion, as I rarely receive playlist links to other video hosting platforms (at least none where a simple wget call doesn't solve the problem.
This little script show-cases one reason, why I like Linux so much: there is always an easy way to extend existing functionality.