Some of the ones that I fell in love with:
I think A Pirate's Guide to First Gradeis my favorite. It is full of fun pirate phrases. It is perfect for introducing the concept of context clues. Don't worry. There is a glossary in the back for all you land lubbers. ;)
My favorite non-fiction book was You Wouldn't Want to Be a Pirate's Prisoner!: Horrible Things You'd Rather Not Know . It had a lot of great tips and some fun illustrations. I highly recommend it for older grades.
Some others that I still want to check out:
Shiver Me Letters: A Pirate ABC
Do Pirates Take Baths?
Pirates Go to School
The Pirates Next Door
There Was an Old Pirate Who Swallowed a Fish
Pirates by Gail Gibbons
Pirates by Mary Pope Osborne
The Pirate of Kindergarten (Richard Jackson Books (Atheneum Hardcover))
What about you? Any favorite pirate books?