The 0-Hecke algebra Hn(0) is a deformation of the group algebra of the symmetric group Sn. We show that its coinvariant algebra naturally carries the regular representation of Hn(0), giving an analogue of the well-known result for Sn by Chevalley-Shephard-Todd. By investigating the action of Hn(0) on coinvariants and flag varieties, we interpret the generating functions counting the permutations with fixed inverse descent set by their inversion number and major index. We also study the action of Hn(0) on the cohomology rings of the Springer fibers, and similarly interpret the (noncommutative) Hall-Littlewood symmetric functions indexed by hook shapes. P α summed over all compositions α of n, where every P α is a (left) indecomposable H n (0)-module. It follows that {P α : α |= n} is a complete list of non-isomorphic projective indecomposable H n (0)modules, and {C α : α |= n} is a complete list of non-isomorphic simple H n (0)-modules, where C α = top(P α ) = P α / rad P α for all compositions α |= n. for their helpful suggestions and comments.