Cobuild grammar pattern series are based on corpora. Producing corpus-based reference books such as grammars and learner dictionaries is a kind of what Leech (1997) calls indrect use of corpora in language teaching.
Now you mentioned collocations. I must say that the only reliale way to extract statistically significant collocations is use corpora (see my posting on "Collocation, semantic prosody and near synonymy" for further arguments). In the language classroom, KWIC concodrances sorted in a proper order also provide a visual aid in learning collocations.
With that said, we have to admit that corpora are not alll powerful. What cannot be done using a corpus-based approach must be done using other methods. But no doubt corpora have certainly changed what is taught and how it is taught in many parts of the world.
For further discussion of the pros and cons of using corpora in language teaching, I would recommend Seidlhofer's (2003) book "Controversies in Applied Linguistics" (section 2), published by the Oxford University Press.