Powering small projects from 120vac line

TL;DR: Controlling a 120V AC line with a relay controlled by an Attiny 45. Want to use the 120V AC line to also power the 5V DC line to the Attiny45. What is the cheapest/most efficent/most practical way to accomplish this?

The whole story:

I'm building a simple infared remote house lamp controller array with a twist. Each lamp relay circuit has one button on the remote, but if you are pointing the remote at the wrong lamp and pressing the wrong button, the lamp relay circuit will kindly forward the button signal to the correct lamp for you via RF signals. The total cost for each circuit is less than $2 when using an Attiny45 as an Arduino, but I'm running into a snag here with supplying power to it.

The circuit will be inside the lamps themselves. I was hoping to tap into the 120VAC running through the relay to the bulb. Problem is, any circuit I can build to regulate 120vac down to 5vdc would cost significantly more than the rest of the circuit and would be pretty bulky (if it involved a standard transformer). Does anybody have any good ideas on how to accomplish this?

I may just get ghetto on it and invest in a bunch of cheapo cell phone usb chargers and steal the guts out of them.

SuperMechaCow:
What is the cheapest/most efficent/most practical way to accomplish this?

Not concerned about safety?

SuperMechaCow:
I may just get ghetto on it and invest in a bunch of cheapo cell phone usb chargers and steal the guts out of them.

if there is room in the lamp, this is the way to go.

http://sound.westhost.com/articles/power-supplies2.htm

I used number 7 for a similar project. There are all sorts of warnings about how you can kill yourself, but I was careful enough that I luckily am still alive.

Yea safety is a concern. I'm not a total newbie but so far my most intense experience with household AC has been assembling a bench PSU and I could probably build a decent xformer/rectifier/regulator PSU from scratch. I can't find any decent transformers for under $5 and I will need to build about a half dozen of these circuits. It would also be very easy for me to assume I know what I'm reading in that link and blow myself up when I least expect it.

Was an awesome link, though. Definitely bookmarking it.

Found some usb wall chargers for about $3 a piece on ebay from China, bringing each circuit to about $5 each. That will probably be what I do.

Found some usb wall chargers for about $3 a piece on ebay from China

I use this sort of charger for some things, but be aware the quality of a lot of these very cheap chargers can be very poor.

They are also very dangerous if you open them up and just use the electronics inside them.

I was intending to just remove the usb and wall plug pieces and recycle the the entire circuit board as-is. The entire project will be in an insulated case.