This is the current version of the original, ground breaking COBUILD corpus. The free access to concordance lines and collocation information has sadly been withdrawn. Now you need to subscribe to access the corpora available although you can have a month's free trial (one per e-mail address). There doesn't seem to be an individual subscription so this is a very expensive tool.

This is a powerful concordance tool which can be used with certain corpora on its website (including German, French and Chinese corpora). It can give you a complete word sketch of a word's collocations, as well as a thesaurus and detailed comparisons of two words. You can also make your own corpus with its WebBootCat tool. An individual annual licence is £50.