Club Cha Cha would be a social Cha Cha, as opposed to competitive or show Cha Cha. It would tend to reflect a more casual, easy-going club kind of feel. You can think of it this way: Club Cha Cha is to ballroom Cha Cha as Salsa is to Mambo.
Josie Neglia has a great instructional video for club Cha Cha, if anyone is interested. You can find it at www.latindance.com.
Ciao,
Jonathan Atkinson