MixMeister Fusion   Allows live DJ performance and allows you to export your completed mix as an MP3 or burned to a CD using the integrated burning tools.   Version 7.2 includes new features like an enhanced timeline, improved time-stretching and support for Mac OS X.    Key feature:   While the current track is playing live, Fusion allows you to load in your next track, preview the transition, edit and beatmatch any part of your mix through your headphones.  Note that this reqjuires a dual sound card.  See the hardware setup pages for information on dual sound cards. 

With MixMeister's label markers, intro and outro anchors and the capability to save 'tweaks', 99% of beat matching can be done before the show or is done automatically as each track is loaded.  MixMeister also has the capability to manually adjust  and very precisely set the transition point for any two tracks.  For my setup laying in new tracks and checking out the transitions while the set is underway is made possible with the Echo Indigo - dj sound card.  Other stereo output cards work in a similar manner.  However, I found the Indigo - dj card easiest and simplest to use with my older laptop.  See the NI Audio 4 DJ page for the NI Audio 4 DJ dual sound card for use with newer laptops.

Fusion also allows you to manipulate tempo, volume, and EQ in real time, on-the-fly. It records all your actions (not just the resulting audio), so you can go back, listen to your mix, and make precise adjustments. 

Fusion's live performance capabilities can be expanded via connectivity with MIDI hardware controllers such as the Numark MixMeister controller and others.

Beatmixing.com forums are full of help for setting up and using the software and hardware.   If I can figure it out with help from the forums, anyone can.

Sony Sound Forge and Acid Pro

http://www.sonycreativesoftware.com/products/soundforgefamily.asp

http://www.sonycreativesoftware.com/products/acidfamily.asp

http://www.peaceloveproductions.com/

I use Sound Forge for tweaking and creating loops for intros and transitions.   These can be saved in a number of formats and used in MixMeister or any other music software program.  Acid Pro and Sound Forge are both great for creating original tracks and loops and for remixing and combining tracks in many ways.  Both programs have extensive tools for manipulating any characteristic of a track or loop.  Peace Love Productions offers all kinds of loop material - free loops and a good selection of CDs.  Very good material for transition building, remixing or building your own tracks.