Torus knot groups are certainly linear.  The universal cover of a torus knot complement is Euclidean space, and the action of the group on this cover factors through "translations on euclidean space" cross $PSL_2(\mathbb R)$.  Both linear groups. 

Generally it's conjectured that all 3-manifold groups are linear.  For all I know, there might be a proof already. See http://mathoverflow.net/questions/108754/what-is-known-about-a-3-manifold-m-when-its-fundamental-group-is-linear