IDJC (Internet Disc Jockey Console) is the app you want to use if you need to run a traditional DJing setup with multiple mics for the DJ plus guests (skype is supported amongst others) and have two decks with which to crossfade and pitch correct mp3s into the mix. In addition it all integrates with jackd so you can output whatever you need to wherever you need it. It's been rock solid for me so far and i can't reccomend it enough. You can read about it here http://idjc.sourceforge.net/

So here are the instructions for a 64Bit Fedora install (Me and Ubuntu are no longer on speaking terms...)

Install some dependencies.

Download and compile lame encoder from here http://lame.sourceforge.net/

If pkg-config cant find the right stuff then export some env vars

Download the idjc source from http://sourceforge.net/projects/idjc/

check these two lines in /usr/local/bin/idjc

add this to /etc/security/limits.conf

Add yourself to the jackuser group

if it moans about not finding libmp3lame.so.0 do this

Tada.