British Parliament (Hansard) 1803-2005
Freely available. This website allows you to quickly and easily search more than 1.6 billion words of text, in more than 7,600,000 speeches from nearly 40,000 individual speakers in the British Parliament from 1803-2005. You can search for words, phrases, collocates (nearby words), and even grammatical constructions. You can also search the corpus "semantically", when you want to find all words with a particular meaning.