Lowest temp I know is -273.15 C, or like you guys say, absolute zero.
Just to add on to glider's comments:
The group led by Wieman and Eric Cornell made the first Bose-Einstein condensate in 1995, at a temperature just 200-billionths of a degree Celsius above absolute zero. Now, with experience, they've learned to make them at the "balmy" temperature of one-millionth of a degree above zero.
http://whyfiles.org/052einstein/bose.html
200 billionths of a degree it seems like we can achieve.
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