XBMC has definetely got reasons to get popular these days.XBMC (Formely Known as Xbox Media Center) is basically a free and open source cross platform media centre to suit all your media needs.
If you are using a linux based operating system like Ubuntu, literally downloading the youtube videos is as easy as just watching it. I mean it when I said it. Anyway here I explain the best and the easiest options I found in downloading the youtube videos.
Weeks ago when I was trying to setup Ubuntu in my pc for the first time, installing new software you need in your new pc would be a impossible process without internet or any Repository DVDs. I managed to get a few resources from net and here I will explain it as a step by step procedure. First you should have another computer which is well connected to the internet or you should have an APTonCD created by someone. Once you install the required softwares with the help of internet connected PC, you could backup all the packages into a CD for using next time.
The first thing one finds when trying to learn GTK is Glade which makes the whole process much easier .Here is the perfect way to get started with GTK gui programming and the collection of best tutorials on net.
When do you think you are ready for creating your own application? GTK and Qt ,the same toolkits behind GNOME and KDE, are the best graphical toolkits fit for this job. Providing the same functionality they have their own advantages and disadvantages.