Where to start for micro controllers (lower level than Arduino)?

alohaduino:
Any tutorial/walkthru URL?
tks!

Sort of.

But you do not necessarily need to upload a bootloader.
You can simply upload your programs directly to the raw chip using the Arduino as an ISP.
And the UNO CAN be used as an ISP even though it says it cannot.
Also I would recommend using 100 ohm resistors between the chip and the Arduino in case one outputs high and the other low on the SPI pins or vice versa.