Heh, I guess there are already plenty of tools out there which do this sort of thing already (never seen them personally, but then I’ve never looked either, heh), but this only took me half an evening to throw together anyway.
Basically, it’s a Python (uses youtube-dl) and PHP-powered web-based YouTube video downloader and converter, you just stick in the URL to a YouTube clip you want to save, and it will download it and offer it for download as an MPEG which you can save on your PC and play in all it’s low-quality glory whenever you want.
Basically it automates the following, which can be run on any Linux PC:
# youtube-dl.py -o myvid.flv http://www.youtube.com/watch?v=123abc # ffmpeg -i myvid.flv -ab 56 -ar 22050 -b 500 -s 320x240 myvid.mpeg
As an added benefit, it stores a complete history of downloaded clips, so you and others can re-download them at any time without having to do the whole fetch/convert process over again. Plus it uses a nifty fake AJAX waiting effect :P.
Requires Linux with ffmpeg, Python 2.4+, and PHP 4.3+.