@foxbrain
The USB asp programmer is a tried and trusted programmer. ATMega48 or ATmega8 either one may be used as a firmware chip and two different firmware .Hex files may be found for each of the same. You need to program the firmware given in respective device with given fuse settings and when programmed, your Programmer is ready to be used when installed with a driver which you'll find in the download package. The Target chip which is to be programmed, is to be conected to the MISO, Mosi, CLk, Vcc and GND pins marked on the connector.
Have a look at this thread where we have discussions about the USB ASP as it may be modified to program 89Sxx chips too.
Cheers
Thaz it..Cheers