In recent years, an increasing emphasis on distributed Web services has emerged in many areas of information technology. Interest has been especially strong in Web GIS (Internet-based geospatial applications) since it is an integral element of the Web 2.0 movement.

One buzzword in this context is Mashup, a mixture of HTML, JavaScript, publicly available application programming interfaces (APIs), and data provided in different formats in order to provide new experiences and functionality in a new application.

In this presentation the relevance of mashups is shown, with special focus on geo-mashuips. The basic technological principles and services are explained and commonly used formats are introduced. Relevant APIs and data sources for mapping purposes are presented, and an assessment is given. Key factors for successful concept and implementation are explained.