In short, I'd like to power Arduino-like devices (small PIC devices as well) run off of a mains socket at 240VAC - which obviously can't be done with a simple wire. I assume I'd need an output anywhere between 3 and 5 volts DC.
I don't want to use a generic plug power supply as they're usually designed for higher current outputs (I'd probably need 500mA at most - the processor and a couple of LED indicators), can cost a reasonable amount and I'd like to up my electronics knowledge/DIY skills by creating something myself (even if it is just a couple of soldering joints).
Also, when I say "best", I mean either the simplest to build or most efficient (or a combination of both).
My apologies for the generic question, I've just never done this sort of thing and I'm not sure how to word it properly.