I use AT89S8252 and ISP feature. For programmer I use aec programmer (parallel port directly connected to ISP pins of 8252 and 2 resistors and one capacitor to reset, it also support at89S51 & 52).
i can post the boot-loader developed by me if u want.
it is a generic one and can work on any 8051 uc.
it can also program the flash chip while downloading.
the gui on pc side is still under development
the architrave is assumed to be von unman type.
Hock