Drive 230Vac load (bulb,fan etc) using microcontroller (3.3V or 5V)
For home automation, you should look into X10:

http://www.x10.com/homepage.htm

X10 interfaces exist to automate just about any part of a house. To control the automation, you can use one of the dedicated X10 panels or implement the X10 protocol on your microcontorller of choice. There are plenty of libraries available for PIC, AVR, 8051, etc.