Corpus of Contemporary American English (Mark Davies BYU)
"The COCA is the largest publicly-available corpus of English, and the only genre-balanced corpus of American English. The corpus contains more than 400 million words of text and is equally divided among spoken, fiction, popular magazines, newspapers, and academic texts. It includes 20 million words each year from 1990-2009, and the corpus is also updated every six to nine months. Because of its design, it is perhaps the only corpus of English that is suitable for looking at current, ongoing changes in the language. The interface allows you to search for exact words or phrases, wildcards, lemmas, part of speech, or any combination of these. You can search for surrounding words (collocates) within a ten-word window (e.g. all nouns somewhere near faint, all adjectives near woman, or all verbs near feelings), which often gives you good insight into the meaning and use of a word."