The hat here is size-able for a young child, say 2 to 6 years old. Please read through to the end of the pattern once before starting for all the sizing details. I will be knitting an adult version in the near future, and will post the figures when I have them, but if you're ready to extrapolate on your own, I'd suggest adding 10 stitches all around, increasing the number of rows by 25-30%, center the chart on the completed back for a guide to placing it on the front as you knit, and see what you get.
A note on wool for felting:
White wool may not felt. If you you knit this pattern with matching black and white Cascade 220, for example, you would get this:
Puckers.
What you need is a wool that began life as white, and didn't have to be bleached to make it pretty. Honest White Wool. That's what I'm talking about here. It is a rare thing. Bleaching alters the surface structure of the fiber and makes it too smooth to bind up when it's submitted to felting process. 
You might have some luck with the Knitter's Review Felt Forum for more resources for Honest White Wool, but as for me, I used Crystal Palace Iceland, because the gauge was a perfect match for a double strand of 220, and it worked very well, as you can see on the right. Both samples were knit with black Cascade 220.
Materials:
3 skeins Cascade 220 in Black (or pink for you urban pirates), used double throughout.
1 skein Crystal Palace Iceland in White
Size 13 needles
Tapestry needle
Hat Back
Using main yarn, cast on 16 stitches. Knit one row. Using cabled or knit-on Cast on, add 2 stitches, turn and working in stockinette, work to the end of the row. Repeat at each side until you have 26 stitches in all.
Now, increase, using your favorite way that doesn't leave a big hole, after first stitch at the beginning of every row until you have 40 stitches.
Then *increase after the first stitch and before the last stitch of the next third row and then similarly on the next fourth row. Repeat from *.
When you have 58 stitches, begin the crown opening. Cast off center 8 stitches and knit to the outside edge. Now working one side only, knit back to the crown opening, turn, and cast off first 2 stitches. Knit to the end of the row. At the same time, make no further increases at the outside edge. Decrease one stitch at the crown opening every other row, until you have 18 stitches. Skip the decrease for the next row, then decrease one more time.
Now you have 17stitches. Work for 6 rows straight, then place stitches on holder for grafting later. Work the other side of the hat back in mirror fashion.
It will look something like this. I do mean "something like". See photos in previous posts for other clues.
Hat Front
Follow instructions for the Hat Back, but incorporate the Jolly Roger chart. Mark the center stitch, and use this as a guide to center the chart on the piece. Begin the chart in the row when you have 32 stitches. While knitting the chart, if you have knit in garter stitch up until now, pay attention to the right and wrong side as garter stitches while changing colours from row to row may be unsightly. You might find it easier to just work the entire chart area in stockinette.
When front is complete, match stitches from front and back pieces and join using either a three needle bind-off, or graft together for a smooth join. With a large tapestry needle and length of the black yarn, using an overhand stitch, lash the top edges together starting about a third of the way up from the join.
Hat Sides
After making this hat a few times, I've been meaning to add one thing.
I think the hat looks best with a tall triangular gusset piece sewn between the front and back of each side, but it's not necessary. If you like, cast on 13 stitches and make a decreasing at each edge every 8 rows until you have on estitch left. Draw the yarn through the last stitch. Center the bottom of the triangle at the join of the front and back brim, and sew the side seams shut.
If you decide to not use the gusset inserts, sew the crown front and back together to halfway down the skull motif, as you see in the picture below, and leave the rest open.
To felt the hat, place in a white zippered pillowcase (see note) and agitate in hot water and a very little soap in a top loading washer for a cycle or two, while checking on the felting progress. When the hat has felted to a pleasing degree, give it a few tugs to even out the shape if you like and allow to dry. My finished dimensions were about 16" across and 9" tall. The initial felted opening would have fit a head that was 19 inches around, but it eased out with some gentle urging by the scissors -- just enough to break the felted bond along the edge -- to fit a 22" head. If you want an even smaller hat, make fewer decreases and leave more stitches on the needles as you work the sides of the crown openings, say, 19 or even 22 stitches.
The mending of an over-zealous slice can be untidy looking, so be gentle at this stage if you choose to adjust the fit. You can also slice through some of the side sewing if you want more ease in that area than the felting left you with.
Note: The pillow case is to protect the inner works of the washer from the snags of wool that will float free as the piece felts. While this is optional, and I know you're ready to do this NOW, I recommend that you either loot one from your partner's pillow (you'll put it right back; it is getting washed after all), or if you have not yet achieved the bourgeois status of such things as napkin rings and pillow protectors, trot down to Kmart right now and pick up a zippered pillowcase for your felting, since one of these items costs $5, and a new pump for the washer can be somewhat more pricey, and you never know about the reliability of your randomly generated repair person. Could be dicey. Just so you know.
Good luck, and send me a picture!
