This Instructable is now depreciated.
Click here for the updated, much improved, version.
This will hopefully show you how to control electronics across the internet using your Raspberry Pi.
It's not the best way to do it, and soon I will update this with a way to use MySQL to do the same thing.
Here's a link to YouTube showing it in action: http://www.youtube.com/watch?v=OCZlfAFcm7Q
For this, please ensure that you have apache with php running on your Raspberry Pi, Instructions can be found here
Also, it would be a good idea to read my previous instructable on general GPIO control, which can be found here