using a triac and a PIC at a wall switch

[Spehro Pefhany]

You physically prevent any possibility of the user touching the
output. If there's a possibility you spend the money to add isolation
(transformer or SMPS with transformer).

BTW, I just used this technique to power a microcontroller from 120VAC
for a fun little project (a 4-channel chaser). It uses an X2 rated
capacitor, a surge-resistant series MOF resistor, and a unidirectional
TVS rather than a zener, so it should be pretty resistant to mains
transients. I used a zener to regulate the 5V rather than a 78x05
regulator.

http://www.speff.com/chaser4ch.jpg

Through-hole technology- single sided board, really retro. ;-) It just
drops into a utility project box.

Best regards,
Spehro Pefhany