I want to build a low cost switch for AC power (120V / 15A max). Eventually would like to control this switch with a micro controller (Possibly 5V / 3.3 would be better)
Lots of options, phsical relays, SSR, power mosfets.. etc. Whats the best suggestion for lowest power / lowest cost?
Good old Relays are still used quiet a bit, they're cheap, reliable and easy to use. Interfacing them to a microcontroller is simply a matter of using a single resistor transistor and a diode.
Solid State Relays can allow you control options like dimming and faster more frequent switching but for many basic application a simple mechanical relay is fine.