Mixxx is an open source DJ tool designed for both professional and amateur DJs alike.
Mixxx allows DJs to mix music live with a clean, simple interface. Futhermore, Mixxx has a number of key features to help DJs in the mix: Beat estimation, parallel visual displays, and support for various DJ hardware controllers.
Beat estimation: Mixxx estimates the BPM of each song to help you beat match.
Pitch independent time stretch: Adjust the tempo of your tracks without changing their pitch.
Hardware support: Control Mixxx with your favorite MIDI devices and hardware like the Griffin Powermate.
Waveform summary displays: Visually see the dynamics of a track, just like with vinyl.
Completely Free: Mixxx was designed by DJs, for DJs, and is distributed freely under the GPL.
Demo : http://www.freewarefiles.com/Mixxx_program_35053.html