Robert Schramm - Educate Towards Recovery is good, though is full of terminology which you have to get your head round (once you do it all makes sense).
It's on the Verbal Behaviour approach of ABA (which we're using), which is a newer approach and focuses on teaching within the natural environment. (Eg at the moment we're teaching ds how to use appropriate language with his peers such as 'what are you playing', 'can I play too' etc through dressing-up and role play such as doctors/firemen/superheroes. It is brilliant fun for ds and he doesn't even realise he's being taught!)
You can work on anything - reducing tantrums or other inappropriate behaviour, aggression, obsessions, repetitive play, expressive/receptive language, toilet-training.... whatever you want the programme to focus on.
We have a programme run through a consultant, who sees us every three/four months, a supervisor (appointed by the consultant) who sees us every few weeks, and tutors who we employ ourselves. We have about 25 hours a week with tutors, both at home and nursery.
It is a bit daunting setting it up if you do it yourself, but once it's up and running it just sort of runs itself.
The organisations Peach and UKYAP will set the programme up for you, but I don't know too much about them (others here will do - search old threads for ABA). Maybe start a new thread about this too.
Funding - we've been totally self-funding so far, but are int he process of statutory assessment for a statement, and are asking for full funding. Doubt very, very much we'll get it and are anticipating a tribunal, and even then don't know if we'll be successful!
Have you thought about applying for a statement yet? If you do, and want to ask for ABA funding you'll need to gather all the info very thoroughly to prove how effective it is, So you may have to prepare for paying for it yourself, at least initially, so you can demonstrate how it's worked compared to any other strategies employed by other agencies (SALT, nursery, outreach etc). Everything is recorded in minute detail so you can clearly show the progress made on specific targets, which is good evidence to show that it's working.
HAve to rush off now but can give you more info about costs etc if you want.
Where do you live? Might be worth joining local NAS group to meet other parents - I've met a few locally who have also done ABA so it's a good way to exchange information.