Books
Here's a list of books that relate to the 680x0 family, both interfacing and programming:
Microprocessor Systems Design. 68000 Hardware, Software and Interfacing, 2nd edition, Alan Clememnts. Pub. PWS-Kent 1992.
I really like this book. I find the descriptions clear and easy to understand. Without this book, it would have been much harder to get my head round the 68681 Duart, as all the datasheets I've seen from the various manufacturers are very badly written.
M68000 8-/16/32-Bit Microprocessors Programmers Reference Manual, Fifth edition, Motorola. Pub. Prentice-Hall 1986.
Not much to say really about this. It's the book I refer to whenever I need full details of a given 680x0 instruction. Unfortunately, it only covers 68000, 68008, 68010 and 68012. I keep looking for one that includes details of the later processors.
Programming the M68000, 2nd edition, Tim King and Brian Knight. Pub. The Benjamin Cummings Publishing Company Inc. 1986.
An okay book that takes you through all aspects of programming devices up to and including the 68020.
Microcomputer Architecture and Programming. The 68000 Family, First edition, John F. Wakerly. Pub Wiley, 1989.
An Introduction to Microcomputer Systems, Architechture and Interfacing, John Fulcher. Pub. Addison Wesley, 1989.
Lots of theory. Covers multiple CPU families, including 68000, up to the 68030.