Recently, when sitting at traffic lights in my 2000 Hyundai Elantra,
I've noticed the idle dropping ever so slightly.  Usually, it runs at
about 800-700 RPMs, but it was dropping about 100 RPMs to 700-600.  The
drops were small and random, so I just shrugged them off thinking I
might need a tune-up soon.

Recently, since fall has arrived, I've been using less A/C and more
windows.  Just yesterday, when sitting in a parking lot after lunch, I
discovered a pattern.

When I shut the A/C off, I no longer saw the idle drop.  Just out of
curiosity, I tried pushing the up button for the windows (even though
they were already up.)  The idle dropped.  Then I let go and the idle
returned to normal.  A/C on, idle dropped.  A/C off, normal.

Could this be something related to my electrical system or am I way off
base here?  I only know the basics about cars, so please include
layman's terms with the technical stuff.  ;)

Two other things I should note.  Might be related, might not be...

My car's reaction to the gas pedal has also been slow lately.  I know
it's not a powerful car, but it used to react to the pedal very
quickly.  Now, it sometimes hesitates for a second or two before it
kicks in.

I've also had chronic problems with light bulbs blowing out (usually
the tail lights.)  The mechanic would catch them during an oil change,
etc., and I'd have them replaced.  Within weeks, the same bulbs might
blow out.

Thanks in advance!