Singular spectral curves in finite gap integration

We expose some applications of the finite gap integration method which involve singular spectral curves. They include orthogonal curvilinear coordinate systems corresponding to spectral curves with geometrical genus zero, finite gap Frobenius manifolds, and soliton deformations of spectral curves corresponding to equations with self-consistent sources. This is an extended version of the talk given at the conference "Geometry, Dynamics, Integrable Systems --- GDIS 2010" (Serbia, September 7--13, 2010).