My mixing software comes from Native Instruments, and is called Traktor, its the digital bit of my setup
Traktor is not the only mixing software you can use, there's also Virtual DJ, M-Audio Torq, Mixvibes, and off course Serato.
The choices are virtually limitless, but, the Traktor light version came with my hardware, and i upgraded it to the full version.
More info about Traktor can be found here
Some Traktor screenshots