We generate new AdS_4 solutions of D=11 supergravity starting from AdS_4 x
X_7 solutions where X_7 has U(1)^3 isometry. We consider examples where X_7 is
weak G_2, Sasaki-Einstein or tri-Sasakian, corresponding to d=3 SCFTs with
N=1,2 or 3 supersymmetry, respectively, and where the deformed solutions
preserve N=1,2 or 1 supersymmetry, respectively. For the special cases when X_7
is M(3,2), Q(1,1,1) or N(1,1)_I we identify the exactly marginal deformation in
the dual field theory. We also show that the volume of supersymmetric 5-cycles
of N(1,1)_I agrees with the conformal dimension predicted by the baryons of the
dual field theory.Comment: 28 pages, 2 figures; v2. typos correcte