Mixxx is free, open source DJ software that gives you everything you need to perform live mixes.
You can install Mixxx 1.9.0 by adding the mixxx ppa and install it using a terminal command. When Mixxx is started for the first time you will be asked for the location where you store your music files. Browse to the location, add the folder and press on the Open button. Enjoy your mixxxing!
To install Mixxx open a terminal window (press Ctrl+Alt+T) and copy+paste the following lines:
sudo add-apt-repository ppa:mixxx/mixxx
sudo apt-get update
sudo apt-get install mixxx
To start Mixxx press Alt+F2 and type: mixxx