Dear sir,

why do you want to build a STANDARD programmer. They come very cheap for most 8051 derivates !

Focus your job on the target board instead of the programmer.

As mentioned by Peter, Atmel has some nice controllers that can be programmed by using a standard PC serial port, 5 volt,a crystal and a MAX232 level convertor. PC software FLIP, etc..

It takes you about 1 hour to get your own programmer to 'work'. Simple breadboard will do the trick.

Try to avoid the work spending on a programmer, cause technology is faster than you ever can keep up.