As corpus building is an activity that takes times and costs money, readers may wish to use ready-made corpora to carry out their work. However, as a corpus is always designed for a particular purpose, the usefulness of a ready-made corpus must be judged with regard to the purpose to which a user intends to put it. There are thousands of corpora in the world, but most of them are created for specific research projects and are thus not publicly available. This article introduces well-known and influential corpora for various research purposes, including national corpora, monitor corpora, corpora of the Brown family, synchronic corpora, diachronic corpora, spoken corpora, academic/professional corpora, parsed corpora, developmental/learner corpora, and multilingual corpora. While most of the corpus resources introduced here are for English, this article also include a number well-known corpora for other languages. The information provided in this article will enable readers to judge whether a particular corpus is suitable for their research purposes, and to find out how to get access the corpus.