mikroElectronic offers a free online book about PIC Microcontrollers. The book is very well illustrated and cleary written with good examples.
While it mostly focuses on using the PIC 16F887 microcontroller with assembly, large portions of the book are also applicable to other PIC microcontrollers. They also sell a print copy with CD for $24.
Its small rule NPRM day (maybe)
2 hours ago