The paper proposes a methodology for collecting “open-source” corpora, i.e. corpora that are automatically collected from the Internet and distributed in the form of a list of links with open-source software for recreating their full text. The result is a random snapshot of Internet pages which contain stretches of connected text in a given language. The paper discusses a methodology for acquiring such corpora, two ways of documenting them (using a set of metatextual categories and by comparison to frequency lists from existing corpora) and their function as benchmarks for comparing results of linguistic inquiry. Experiments with a variety of languages show that Internet-derived corpora can be successfully used in the absence of large representative corpora that are rare and expensive to build.