You might know that INdT released Youtube plugin as free software, it's great feature-wise and touches almost every part, providing new models, views and controllers, those with complex use cases like threaded models so GUI will not block during HTTP requests and even options menu.
That's cool because one can do lots of things (and some users are already showing us some nice plugins!), but we still need some base text introducing people to the concepts, with smaller code, so here it is: Canola URLBookmark source code and text.
This introduces you to some concepts, explains about "plugins.info" and how plugins are loaded and in the end you have a list of URL to play. Of course this hard coded list of URL is on purpose so you take some time to change it to something more useful. If you ask me, I'd like to see UPnP, MPD, Samba, Avahi, Shoutcast and lots more.. I did my part, everything you need to know is there, now it's your turn. ;-)