This book contains papers growing out of recent work of the Singularity Seminar at Moscow State University. The main topic of most of the papers is the analysis of singularities of discriminant hypersurfaces formed by the degenerate objects in different spaces of mappings. Among the topics covered are: the space of mappings of the circle to three-space; invariants, bifurcations, and classifications of plane curves; algebraic invariants of the Morse complex; complex boundary singularities; spaces of morsifications of singularities; and the number of singular points on a complex projective hypersurface.