How would I charge, say, an iPad with the standard U.S. adapter and cable?
(Asked on behalf of a twitterer.)
Indonesia uses European-style two-pin round plugs ('C'-type is the most common variant found):
Voltage is at 220 V 50 Hz (as opposed to 110 V 60 Hz in US). Most modern electronic equipment that has auto-sensing capability should work without needing a voltage converter, you will need a plug adapter though which can buy cheap online. As for Apple products specifically have a look at this question.
What I do when I need confirmation is to check this website:
It has an EXHAUSTIVE list of each and every type, the voltage and the countries that use them. It's been handy for some of the stranger countries I've been to and hasn't failed yet.
Myself, I have a multi-adapter. The only country it doesn't seem to handle is South Africa, which has 3 giant prongs - bigger than the UK ones!