AVR-Chat

I was going through the Digi-Key catalog to stock up on some components for
upcoming projects so as to avoid the $25 minimum and I need some guidance.

I'd like to purchase some opto-isolators to be used to buffer AVR digital
outputs to field wiring and also to buffer digital field wiring inputs.  All of
these are "status' I/Os so no hi frequency stuff involved.  I expect all to be
in the 3v to 5v range, low current.

1) There are a mind boggling number to choose from (transistor, darlington, fet,
etc.).  Can you give me some guidance as to a 'general purpose' device for this
type of use and what general conditions the device would not be suitable.

2) If driving a low current PC board relay is it good practice to connect the
coil directly to the AVR (w/snubber diode) or should I use a opto here too?

3) I think I've seen reference to "opto-isolators" and "opto-couplers".  I
assume these terms refer to the same device?

4) Is there a good web resource for MCU interfacing practices so I don't have to
bug you guys with this kind of stuff?

5) I also have a need to drive a 12vdc motor (around 1A) using the PWM (speed)
and direction from an AVR.  Can someone recommend an H-Bridge module or web
circuit diagram resource?

BTW: My applications are personal interest, not production.

Thanks,

Chuck Hackett