MashMaker is a web-based tool that makes it easy for a normal user to create web mashups by browsing around, without needing to type, or plan in advance what they want to do. Like a web browser, Mashmaker allows users to create mashups by browsing, rather than writing code, and allows users to bookmark interesting things they find, forming new widgets -- reusable mashup fragments. Like a spreadsheet, MashMaker mixes program and data and allows ad-hoc unstructured editing of programs MashMaker is also a modern functional programming language with non-side effecting expressions, higher order functions, and lazy evaluation. MashMaker programs can be manipulated either textually, or through an interactive tree representation, in which a program is presented together with the values it produces. In order to cope with this unusual domain, MashMaker contains a number of deviations from normal function languages. The most notable of these is that, in order to allow the programmer to write programs directrly on their data, all data is stored in a single tree, and evaluation of an expression always takes place at a specific point in this tree, which also functions as its scope. Categories and Subject Descriptors D.3.2 [Language Classifications]: Very high-level languages; H.4.3 [Information Systems Applications]: Information Browsers General Terms Languages, Human Factors, Design, Management Keywords Mashup, web, end-user, browser