Carl Rytterfalk, a professional digital photographer and whose site I frequent, has put up a guide on his website on how to shoot pictures in a night club. This is a pretty good guide even if you are doing low light photography.
It lets you use a flash and brighten up a seen without getting that over bright in-your-face highlights a lot of flash pictures have.
Plus, if I can take photos like this, 
at 1/8 shutter speed then I have to try this out.
Find out more at this link
and even more at the DPReview Sigma Forums site
http://forums.dpreview.com/forums/readflat.asp?forum=1027&thread=26265198
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