The Collaborative International Dictionary of English v.0.48:

Untaken \Untaken\
   See taken.

Moby Thesaurus II by Grady Ward, 1.0:

18 Moby Thesaurus words for "untaken":
   abandoned, available, deserted, forsaken, free, godforsaken, open,
   tenantless, unfilled, uninhabited, unmanned, unoccupied, unpeopled,
   unpopulated, unstaffed, untenanted, untended, vacant