For SuperCollider there's a book which is not out yet (I have read a draft and found it excellent, especially for beginners) but it should be out soon.
My old roommate was recruited to write one of the chapters (on language internals and his CocoaCollider bridge), but last I heard MIT Press had dropped the project.
IIRC it would have been the first supercollider book.
You can try to send an email to one of the authors: http://www.music.utah.edu/faculty/faculty_a-z/david_michael_...
He used to send a pdf of the draft version if you asked him, but since the printed book is due soon (by MIT press) I don't know if this is still true.
There's also 'The Theory and Technique of Electronic Music' by Miller Puckette (the author of Pure Data):
http://crca.ucsd.edu/~msp/techniques.htm
The examples are, obviously, in Pure Data. But it is an excellent book and all the concepts can be applied to any synthesis language/tool.
For Csound there's 'The Csound Book' by Richard Boulanger (MIT Press):
http://csounds.com/shop/csound-book
This is also excellent. Disclaimer: the author is a friend.