how to connect the ISP to the ATmega48

Never mind, some helpful folks on the avr-chat mailing list, plus some
more creative Googling, eventually turned up the documentation I needed.  
I'm still amazed that Atmel didn't think it important to include the ISP  
user's guide with the device, since they were including a CD anyway...  
but I'm starting to think that the documentation is kept intentionally
hidden to keep away the unfaithful.  :)

Best,
- Joe

     Atmel has a good line of microcontrollers, and the free tools do everything
necessary and are well integrated, but finding all the information necessary
to make everything play together is excessively difficult.

     I'm currently struggling with a situation where AVR Studio's programming
feature can talk to a board via the JTAG port, but the debugging system
can't connect properly.  See

http://www.avrfreaks.net/index.php?name=PNphpBB2&file=viewtopic&tP472

It's probably some configuration issue, something involving installation
options, or something else dumb like that, but I haven't been able to
make it work yet.

                    John Nagle

     Found out what was wrong.  Low power supply voltage.  The board
I'm using needs 12VDC or 9VAC before the +5 supply comes up properly.
(Yes, that's wierd, but look at the schematic.  Note the zener
diode in the power circuitry at the upper left.  They wanted
12VDC for the Dallas 1-wire interface, and get 5 VDC from that.
So they put a 3.3V zener diode in to drop the voltage before
the 78L05 regulator.)

http://microcontrollershop.com/Images/avr-mt128-sch.gif

With only 9VDC in, the processor comes up, but the +5 supply
is around 4.5V.  The AVR will happily work at that voltage.  But
the ZM33064 reset controller senses it as a power fail and holds
the processor in reset.  In that state, it can be programmed,
and talked to over the JTAG port, but any JTAG function that requires
bus traffic fails.  Hence the wierd "programs but won't debug" symptoms.

                John Nagle