An excelent book on programming the 18F
 

Applying PIC18 Microcontrollers: Architecture, Programming, and Interfacing using C and Assembly by Dr Barry B. Brey from DeVry University..

Takes you from knowing nothing to full development in Microchip "C". Very well organize and full of complete examples on I/O and Interrupts.

Recommend for both new and older programmers...

ISBN: 0-13-088546-0, over 500 pages and a bit pricey at $112

authors page: http://members.ee.net/brey/p10.htm