  We develop a low-energy effective theory for spin-1/2 frustrated two-leg
Heisenberg spin ladders. We obtain a new type of interchain coupling that
breaks parity symmetry. In the presence of an XXZ-type anisotropy, this
interaction gives rise to a novel ground state, characterized by incommensurate
correlations. In the case of a single ladder, this state corresponds to a spin
nematic phase. For a frustrated quasi-one-dimensional system of infinitely many
weakly coupled chains, this state develops true three dimensional spiral order.
We apply our theory to recent neutron scattering experiments on $Cs_2CuCl_4$.
