PICTail(tm) Plus is the name that Microchip uses for the expansion socket offered by the Explorer16 boards. It is one of the easiest and most flexible options available for prototyping out there. All the signals from a 100 pin PIC microcontroller are grouped logically and conveniently in three sections so that if only a few signals are required a smaller board can be arranged. The edge of any PCB can be quickly transformed in an inexpensive (as in free) connector as soon as you realize that all it takes is a set of 1mm spaced traces (gold plating is an option you might consider for longevity). NOTE that all connections are clearly documented in the appendix of the Explorer16 User Guide (DS51589) .
The AV16 board that I developed to support the code examples of the book is only one example of PICTail Plus expansion board, on microchiDIRECT you will find many other options to support: IrDA, Graphic displays with touch sensing, Ethernet, SD Cards and more.
But my all times favorite is the simplest one of all: AC164126 also known as the:
Prototype PICTail Plus board
For $20 you get 3 (three) boards actually. All the signals are accessible in a standard spacing four row line up with silk screen call outs. Get your soldering irons warm!