This volume contains 21 research and survey papers on recent developments in the field of diophantine approximation. This includes contributions to Wolfgang Schmidt's subspace theorem and its applications to diophantine equations and to the study of linear recurring sequences. The articles are either in the spirit of more classical diophantine analysis or of geometric or combinatorial flavour. Several articles deal with estimates for the number of solutions of diophantine equations as well as with congruences and polynomials. Furthermore, the volume contains transcendence results for special functions and contributions to metric diophantine approximation and discrepancy theory. The articles are based on lectures given at a conference at the Erwin Schr?dinger-Institute (Vienna, 2003), where many leading experts in the field of diophantine approximation participated.