Sorry I've been a while replying to these questions - had a tough week last week and next week isn't going to be any better...
dcmbarton - there is a book which covers Kodaly, Dalcroze, Orff and an American approach (forgotten the name of it!). I don't have it but it's one I've been meaning to get for ages. It's called 'Teaching Music in the 20th Century' and it's by Lois Choksy, Robert M. Abramson, Aron E. Gillespie and David Woods. It's published by Prentice Hall and the ISBN number is 0-13-892662-X.
The Vajda (pronounce Voi-da) books are a bit dated, especially in terms of repertoire, but Cecilia (who was my first Kodaly teacher) was a pupil of Kodaly herself and certainly knows her stuff. There are some very good suggestions in both books (Book 2 is a continuation so probably most appropriate to secondary or more experienced younger children).
It is almost impossible to learn about these approaches purely from a book. Could you learn how to play a violin by reading a book about it???! Music is such a practical subject and really has to be experienced!
As noodle discovered, having seen the work in practice it is now easier to understand what is being talked about in the books.
The Lucinda Geoghegan books are wonderful. The 'Singing Games and Rhymes for the Early Years' is a great resource - masses of repertoire and it is also very clearly indicated what the skills and concepts are that are being taught unconsciously.
(Her 'Singing Games and Rhymes for the Middle Years' has just come out and is fab too

).
However, if you want to know how to go on from the musical experience to the 'making conscious' stage then you need 'The Kodaly Method' by Lois Choksy/the Vajda books/Michael Stocks' and Andrew Maddox' Growing with Music, Teachers' Books 1 and 2A.
None of these is ideal and all have their shortcomings, but they are the best that are around at the moment.
We are currently working on developing a musicianship set of exams (we've done as far as Level 4 - phew!) and when we've done the exam criteria we will start to work on the curriculum - eventually we will produce books and other teaching materials. We hope to get accreditation for these exams, probably from Trinity Guildhall.
Unfortunately, due to lack of time to get all this done, I think it's a case of Watch This Space as to when said books will be produced....
Hope this is helpful. Please ask if I can help any more.
And - for anyone wanting to dip a toe in the Kodaly water and start to see what it is all about, don't forget the Cambridge course on Sunday 27th November!
There's also a great course next weekend in Godstone, Surrey, for KS1/2 teachers.