A winter's vest

Yarn: Mark's & Katten's Sarek.  100% wool. 
50 g = 50 meters.  Used 8 skeins for a total of 400 meters.
12 stitches x 17 rows = 4 x 4 inches (10 cm)
I've used color nr. 1924.

Needles: 6 mm.

Size:  Womans medium.
Measurments:  width over hips 105 cm.  Length from shoulder to hip 57 cm. 

Right side of front:
Cast on 44 stitches.  I used long tail cast on.
Knit stitches for 4 rows making bottom edge.
Knit stitches on right side, purl stitches on wrong side (stockinette stitch) for 15 cm, ending on a wrong side row.

On right side: knit 2, ssk, knit the rest of the stitches on the row.  Repeat every right side row until 32 cm, approximately 16 times.

On right side: knit 2, ssk, knit the rest of the stitches on the row every other right side row.  Repeat until 20 stitches left on needle. 

Continue stockinette stitch until 57 cm (or desired length of vest).  Cast off.
Front, left side:
As right side, mirror image.

Back:
Cast on 73 stitches.  Knit 4 rows to make bottom edge.
Stockinette stitch until 53 cm. 
On right side of vest: knit 25 stitches, cast off 23 stitches, put remaining stitches on a yarn or keep on needle while shaping shoulder.
On next right side row: cast off 3 stitches towards the neck.
On next right side row:  cast off 2 stitches towards the neck.
Knit until 56 cm.
Cast off.
Repeat on other side, mirrored.

Sew shoulder seams and 25 cm of side seams measuring from the bottom edge. 

Pick up stitches along neck lining starting from the bottom edge of one front piece going along the neckline and continuing down the other front piece to the bottom edge again.  Cast off using jeny's surprisingly stretchy bind off.  Use the same method to edge the arm. (Do not use this method for shoulder cast off, it is too stretchy and the shoulder will bulge)

Now fit the front to your measurments, slide the front pieces so they fit your body overlapping one over the other.  Sew seams on sides and bottom, making a small pocket in front of the vest, perfect for your iPod.

Good luck! 

Do you want to make another size?
This is how I did the math to fit me, I'll walk you through it so you can make it a perfect fit  for yourself:

The front looks like this, roughly:

Look at the pictures of the vest above, you can tell by the pictures how much the front overlaps.  How far do you want your vest to overlap?  How big do you want your pocket?  Measure how wide you want the bottom of your vest from the side seam to the end of the overlap.  Take this measurement and do the following math:

4 inches = 12 stitches (OR how many stitches per 4 inches your yarn and your knitting makes)  this makes 3 stitches per inch.  (12 divided by 4 = 3)  This time we're lucky to have an even number, if it does not turn up even (could be 5,736 stitches per inch) do the math with at least 3 decimals to make sure the measurement will work right!

Let's say you want your front piece to be 15 inches: 3 stitches per inch x 15 inches= 45 stitches.  So cast on 45 stitches + 2 (the extra two stitches are  edge stitches and will be used when sewing it together)

Knit according to the pattern straight up for as long as you want the overlap (and/or pocket) to be high, start decreasing stitches according to the pattern.

Where the pattern says "or the desired length of the vest"  make sure the vest is the right length for your body.  If you are extremely short you might want to decrease faster than the pattern says, while you are knitting place the front to your body and see if it looks/feels right.  Shape shoulders according to pattern.

Back:

Measure how wide you want the vest to be at the bottom, the back is only one piece so measure from side seam to side seam.  I measured my hips at my widest all the way around and divided by 2.  Do the same math as above but this time use the new measurement.

The back is basically a big square until you get to the neck.  Knit straight up until you have 3 cm (1 1/4 inch) left until the back is as long as the front.  Shape shoulders according to pattern.

Tip:
If I was to make this vest over again, I would make it a little bit longer.