We obviously should all turn on our anchor light at night when aboard, but another nice and easy addition to lighting your boat at night is to install some cheap, simple to operate solar garden lights.
We have added one to each corner of our Lightwave 38 catamaran "Sana Solia". They add to the security of the boat at night, particularly during the week on a swing mooring when people are moving around at night amongst moored boats.
Plus they serve as a nice identifier of your boat when you come back from sundowners or visiting other boats.
$22 for a bunch of ten from any good hardware store.