KDE

I never thought I'd be having so much fun with KDE and FOSS Software as a whole. Its such a good way to learn things and contribute to something which is really beautiful.
In January, I was studying Qt because I found it very interesting, and its cross platform nature really made me to plan serious development.
Then I started to use KDE, which has a very intuitive interface for users. But here comes the real benefit - KDE is a Free Software, so anyone can contribute to the system and improve on it.