VirtualDJ - Virtual DJ Software - MP3 and Video mix software for DJs
Mixxx - The most powerful free DJ software in the world.
Zulu DJ Software - Zulu DJ Software is the best tool for singers and musicians.
Mixmeister - Create custom party mixes, burn CDs, or add special effects to MP3s with this line of DJ software for the novice and pro. Offers free trials and user community.
VJ6 - If blending music is your essential thought process, you might need to search somewhere else for your DJ blending software.
FL Studio - Image-Line's FL Studio, now on it's 12th version, is a well-known music production suite and the most popular beat processor on the market, due no doubt to its longevity. Read more about FL Studio.