Homepage: http://www.qtsoftware.com/
What is Qt?
Qt is a cross-platform application and UI framework. It includes a cross-platform class library, integrated development tools and a cross-platform IDE. Using Qt, you can write applications once and deploy them across many desktop and embedded operating systems without rewriting the source code.
As you know that in the Information Technology field, Visual Studio from Microsoft is the most popular when we were in our universities, so we should learn how to use such complicated IDE and how to program, … Actually, it is very difficult for the beginner because Microsoft always publics new version with addition functions we not always use. Now it becomes very heavy. And what will happen if we use Linux OS ?
When I change to Linux and get used to study Open Source softwares, I found out that QT Programming is the best choice and change my mind 
) and never use Vistual Studio again . It had a lot of advantages:
1. A cross-platform application: I can write a source one time and compile cross-platfrom to make it run on Windows, Mac, Linux, .. without rewrite again. This is the best trend of choosing software nowadays.
2. It is free . QT software was released under several open source license: LGPL, GPL and commercial licsense and now it opens for community contributions.
3. QT have UI framework so it supports a lot of functions like OpenGL, … so you can create a lof of great applications
4. QT now have Qt Jambi for Java programming and QT Designer, QT Creator, …
5. More and more …
Who use QT ?
I can tell you that a lof of peopel change to use Qt. You can see some demo in their website:
And do you know that the popular desktop environment KDE made by QT
And more in QT in use
Download and study
Now, we know exactly what should we go now by going to Download section and start: http://www.qtsoftware.com/downloads
and go to the tutorial section.
Change your mind and get fun !