This is a list of the most commonly used corpora or concordance tools that need a subscription.
1) Collins WordBanks Online http://www.collinslanguage.com/content-solutions/wordbanks
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 The free access to concordance lines and collocation information has sadly been withdrawn.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.
2) Sketch Engine http://www.sketchengine.co.uk/?page=Website/LandingPage