A child's nursery rhyme whose origins lie in the days when pirates would have to recruit men in creative ways. "Sing a Song of Sixpence" goes back to the days of Blackbeard.

Sing a song of sixpence / A pocket full of rye
Blackbeard's crewmen received a sixpence as a day's wages, which was pretty good money back then. They would also receive a "pocket" (a small leather bag) full of "rye" (whiskey).

Four and twenty blackbirds / Baked in a pie
The "blackbirds" are Blackbeard's crewmen, who would feign distress in the open sea and wait for passing ships to offer help. "Baked in a pie" refers to the element of surprise.

When the pie was opened / The birds began to sing
Referring to the previous line; the crewmen attack the unsuspecting ship.

Wasn't that a dainty dish / To set before the King?
The King is Blackbeard, and the dish is spoils from the other ship.

The King was in his counting house / Counting out his money
A subtle recruiting line, this means that Blackbeard has enough money to pay for new crewmen.

The Queen was in the parlor / Eating bread and honey
The "Queen" is Blackbeard's ship, "The Queen Anne's [Revenge". The "bread and honey" is loot.

The Maid was in the garden / Hanging out the clothes
According to snopes.com, "The use of the word "maid" indicated that the location/route of one or more prize ships was known, and they were going to be specific targets of the upcoming cruise (this greatly enhancing the probability of the crew's collecting prize money). The waters around the Carolinas down to the Caribbean were referred to as the garden, as this was an area where pirates would often cruise for easy pickings. "Hanging out the clothes" meant the targeted ship was already at sea or just about to leave port (thus its sails -- or "clothes" -- have been hung)."

When down came a blackbird / And snapped off her nose!
The crewmen brag about their plans to take the prize ship - "snap off her nose!"