Ian writes “This ‘instructable’ covers my new design that programs 8/14/18/28/40 pin PICs. The circuit is based on the JDM2 programmer, with two enhancements: clock and data line filtering; selectable programming voltage. The ZIP archive contains all the project files. Schematic layout for an updated JDM2 PIC Programmer. Includes clock & data filter, Vpp voltage divider for modern PIC microcontrollers (eg USB PIC 18F2455/4455).” Link.
HOW TO – JDM2 based PIC Programmer