The accepted value for the speed of light in a vacuum is precisely 299,792,458 meters/second.
This value is derived from two other defined values -- the exact value of a second is "9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom" and from the meter being defined as the distance light travels in a vacuum in 1/299792458 of a second.*
In a Bose-Einstein condensate, the speed of light has been made to go as slow as 17 meters/second.
* - in other words, a meter is defined by the speed of light in a vacuum and not the other way around.