Thanks. I can't tell if the compressor is running, except I suspect it is b/c pressing the A/C button causes something to happen (something is drawing on the power). I used a Haynes manual and some web-based A/C diagrams (Camry-specific) to check things like was the belt slipping, etc., and the only item that I can see/identify is the sight glass for the refrigerant. I see nothing in it, but on the other hand, and this is weird, the A/C started working again yesterday! Just as it had before. No idea what caused it to fail on Friday, and no idea how that failure could be "reversed" just by letting it sit overnight.
Meanwhile I will keep monitoring it. For 12 years old I don't expect perfection, but A/C is a must where I live (Tennessee).
Again, thanks for the replies everyone.