Toby Manning has written a Guide to Teaching Go (PDF).
Information about Teaching Beginners is also available in Chapter 4 of the Club Organiser's Handbook.
We also have some advice for those intending to run a Teaching event.
In addition we have equipment and other literature that you can borrow/use. See here for the current status.
There's also to a dedicated KGS account that we use for teaching purposes (to Association members only).
Please note that we have an Accreditation System for those who wish to teach in the UK.
We have much helpful advice for those who wish to run demonstrations of Go, start a new club or run one, or run a tournament via our Organisers page. Some of this information is accessible only to members of the Association, so if you aren't one why don't you Join our community?