Why can't I use an optocoupler to drive an AC circuit using the arduino digital pins?
Use it with Triac.  I use MOC3020 + BT138 + 330 and 510 Ohm resistors.
It works good as relay and in dimmer scheme.
Scheme is here 
http://cyber-place.ru/attachment.php?attachmentid=1030&amp;d=1370462030