Controlling Devices that plug into the mains

I recently programmed some fairy lights to turn on when a button was pressed on a remote. I was wondering how this could be done with devices that plug into the mains like desk lamps and electric heaters. Any advice?

Use an optically isolated SSR module.

Or a regular relay.
I made a couple of shields with indicator lights, Uno and Mega size (and one that is standalone, need to assemble one for display, basically the Uno less the header part).
The Uno & standalone use a shift register to drive the relay coils, and the standalone will be easily daisychainable
Here the Uno drives a bunch of Christmas lights - the relay contacts were put in series with the hot lead of the lights.

Could you send a link for an appropriate relay?

Here:-
SSR

An easy way is to use a remote controlled power outlet.
Some come in packs of three with one remote.
An Arduino with 315/433Mhz transmitter can act as a second remote control.
Leo..

http://www.amazon.com/BaiHuang-RS-211-Switch-Wireless-Remote/dp/B0000ERN8H

I have used the Power Switch Tail a few times: Information.com People Search | Free People Finder & White Pages - Locate Anyone

You can buy them pre-assembled or as a kit you solder yourself. Either way, they are rated for mains and are enclosed, with a terminal for connecting your microcontroller.

Power Switch sell a number of models, so you should check you get the correct version for your country's mains voltage and expected amperage. They were relay based but the newer ones use power SSRs.