Residential power can be dangerous, it can kill you. Stay away from these projects unless you know exactly what you do.

LED Home Lighting Projects

How to connect LEDs to AC (no separation from mains = dangerous)

This is an inexpensive circuit that powers a cluster of 18 series-connected LEDs from 230V AC. The 120 V AC version uses different component values.
Losses of this circuit are minimal but there's no separation from the mains. Be sure to isolate the circuit (inclusive the LEDs) well.
The 1M bleeder resistor is not needed for this circuit to work. However, it discharges the capacitor after the circuit has been separated from mains, thereby minmizing the chance of an electric shock.

18 LEDs connected to 230V AC

Using a transformer to power LEDs from AC (rather safe)

This version powers 18 series-connected LEDs from AC, using a transformer (a wall wart) to reduce the mains voltage to a safe value (24 V).
This is nice for outdoor accent lights, because a safe low voltage net is used to distribute the power outdoors while the transformer is installed indoors.
Multiple such lights can be fed by one transformer

18 LEDs connected to 24V AC