The subject of this work is the theory and practice of modern functional programming. The authors not only consider what is achievable with currently implemented languages such as Haskell, Opal, ML, etc., but also point out current developments. On one hand, advanced programming techniques are presented, such as the use of infinite data structures, parsers as higher-order functions, approximation algorithms, solving systems of equations, and more. On the other hand, language concepts are discussed, such as a systematic form of modularization or particularly expressive and flexible forms of typing. A special emphasis is placed on the integration of various paradigms, such as the connection with concepts from object-oriented, concurrent, or constraint-based programming.