KDE (K Desktop Environment) is a Qt-based desktop environment as well as a suite of cross-platform desktop applications. Its latest desktop environment is KDE Plasma 5.
Screenshot of KDE Plasma 4:
KDE is a well-known Qt-based desktop environment, that comes with its own suite of application software.
The range of options is just incredible. It can use a traditional task bar, a unity-like dock, any number of panels.
Very easily modifiable
To get new wallpapers, widgets or themes one can go under System Settings and press the "Get more" button, a dialogue will pop up and all that you need to do is press the "install" button, that it.
They can be used on the desktop or in the panel.
A way to organize your workspaces based on activities.
┃ │ Required │ Recommended ┃
┃ Processor │ 1 GHz (x86) │ Better than 1 GHz (x86)┃
┃ Memory │ 512 MB │ 1 GB ┃
┃ HDD capacity │ 4 GB │ 10 GB ┃
┃ Video card │ VGA @ 640×480│ VGA @ 1024×768 ┃
Note: If "Desktop effects" are desired, a supported GPU is required.
How to install
Alternatively, one can install it from the official image (.iso) that can be downloaded at this page.