Slides of some talks:

Declarative Multi-paradigm Programming
Invited tutorial at the 23rd International Workshop on Functional and (Constraint) Logic Programming (WFLP 2014), Wittenberg, 2014
Available: PDF

Multi-paradigm Declarative Languages
Invited tutorial at the International Conference on Logic Programming (ICLP 2007), Porto, 2007
Available: PDF

Overlapping Rules and Logic Variables in Functional Logic Programs
Talk at the International Conference on Logic Programming (ICLP 2006), Seattle, 2006
Available: PDF

Von Mozart zur Informatik (From Mozart to Computer Science, in German)
See here for more details

Declarative Programming with Function Patterns
Talk at the International Symposium on Logic-based Program Synthesis and Transformation (LOPSTR'05), London, 2005
Available: PDF

Declarative Programming with Persistent Information
Talk at the Oregon State University, Corvallis, Oregon, 2005
Available: PDF

Observing Functional Logic Computations
Talk at the Sixth International Symposium on Practical Aspects of Declarative Languagese (PADL 2004), Dallas, 2004
Available: PDF

Declarative Multi-Paradigm Programming in Curry
Talk at the University of Linköping, 2003
Available: PDF

Functional Logic Design Patterns
Tutorial at the 6th International Symposium on Functional and Logic Programming (FLOPS 2002), Aizu (Japan), 2002
Available: PDF

High-Level Server Side Web Scripting in Curry
Talk at the Third International Symposium on Practical Aspects of Declarative Languagese (PADL 2001), Las Vegas, 2001
Available: PDF

Multi-Paradigm Programming
Tutorial at the European Joint Conferences on Theory and Practice of Software (ETAPS 2000), Berlin, 2000
Available: PDF

Multi-Paradigm Declarative Programming in Curry
Invited talk at the 10th Benelux Workshop on Logic Programming (Benelog'98), Amsterdam, 1998
Available: Postscript PDF

Demand-driven Search in Functional Logic Programs
Talk at the 13th Workshop on Logic Programming (WLP'98), Vienna, 1998
Available: Postscript

Multi-Paradigm Declarative Programming
Invited tutorial at the International Logic Programming Symposium (ILPS'97), Port Jefferson (New York), 1997
Available: Postscript

A Unified Computation Model for Declarative Programming
Invited talk at the 1997 Joint Conference on Declarative Programming (APPIA-GULP-PRODE'97), Grado (Italy), 1997
Available: Postscript

A Unified Computation Model for Functional and Logic Programming
Talk at the 24th Annual SIGPLAN-SIGACT Symposium on Principles of Programming Languages (POPL'97), Paris, 1997
Available: Postscript

Tutorial on Curry: A Truly Functional Logic Language
Second International Fuji Workshop on Functional and Logic Programming, Shonan Village (Japan), November 1996
Available: Postscript

Functional Logic Languages: Basic Concepts and Operational Semantics
Tutorial at the Advanced Seminar on Foundations of Logic Programming: Semantics, Extensions and Applications, Valencia, 1996
Available: Postscript

A Parallel Narrowing Strategy
Talk at the Workshop on Functional and Logic Programming, Rauischholzhausen, 1996
Available: Postscript

Curry: A Truly Functional Logic Language
Talk at the ILPS'95 Post-Conference Workshop on Visions for the Future of Logic Programming, Portland, 1995
Available: Postscript