The recent emergence of mashup tools has refueled research on end user development, i.e., on enabling end users without programming skills to compose own applications. Yet, similar to what happened with analogous promises in web service composition and business process management, research has mostly focused on technology and, as a consequence, has failed its objective. Plain technology (e.g., SOAP/WSDL web services) or simple modeling languages (e.g., Yahoo! Pipes) don't convey enough meaning to non-programmers. We propose a domain-specific approach to mashups that "speaks the language of the user", i.e., that is aware of the terminology, concepts, rules, and conventions (the domain) the user is comfortable with. We show what developing a domain-specific mashup tool means, which role the mashup meta-model and the domain model play and how these can be merged into a domain-specific mashup meta-model. We apply the approach implementing a mashup tool for the research evaluation domain. Our user study confirms that domain-specific mashup tools indeed lower the entry barrier to mashup development.