AVR-Chat

Hi, I'm probably the oldest living active programmer in Australia and
have decided to have a go at AVRmega16's before I die - hopefully
using Bascom basic.
I have done a lot with VB6 and assembly with the old 6502's 25 years
ago but can't find anywhere any concise info on how to structure the
AVR programs and integrating the various sub-routines, interrupts etc.
It all seems so disjointed and every article I have found so is
written by someone who assumes I know what they know. (Like Microsoft
help screens of the past)
Can anyone point me to a good step by step starting guide on how to
compose a simple program to say accept a few switch inputs and output
to a few leds while displaying information from the EEprom on an LCD
depending on what switch is pressed?
With the old 6502 I would have used interrupt routines for the
switches and had a loop polling the inputs and simply written to
output port addresses with an indexed address looking up data
depending on the switch number.
I can't seem to rationalise this to the AVR or is it done another way?
Thanks Ted Smith