Wild Blue Flax, a native species, has been added to the USWildflowers database (08/06/2010.)  Scientific name is Linum lewisii.  This plant also is known by the common names Lewis Flax and Prairie Flax.  Photo below was taken in Ada County, ID, on the road to Lucky Peak on  06/14/2010.

Blue Flax, Lewis Flax, Prairie Flax - Linum lewisii