MASON BEES ARE WELCOME IN THESE HERE PARTS

 
From Gardener's Supply Company:

Boost your garden's productivity by providing a happy home for peaceful, non-stinging Mason bees. Slightly smaller than honeybees, Mason bees are incredible pollinators. Each one visits as many as 1000 blooms per day — 20 times as many as a honeybee! Hang this natural bamboo house against a tree or wall where it will get morning sun and attract bees. Female bees fill the bamboo tubes with their eggs, and nectar and pollen for the young to eat.

Price: $14.95.

On a related note, read this article from the NY Times about the serious threat of bees vanishing and why it could be helpful to do your part.