Microcontroller + Triac without an optoisolator
Depends what the micro is powered from and referenced to. You can run the micro on the live side. However, you give yourself a big problem in attaching debuggers and programmers to the micro, because the 0V side of the programmer usually goes to mains earth through the PC power supply. An isolated USB hub can help. Be very careful with this type of circuit - I know of at least one blown up motherboard caused by this type of work, and there is risk of electrocution.