This is how mine turned out. It looks pretty good and fits my 14in ultrabook with a little wiggle room. It could probably fit a 15in laptop without any problems. I may line it with fabric to make it sturdier in the future but as it stands, this looks and works pretty good for now.
light worsted weight yarn (2 colors)
Stitches & Abbreviations Used
dc - double crochet
ch - chain
sts - stitches
sl st - slip stitch
1. With color A, Chain 75 (to make shorter or longer, add or subtract 7 stitches)
2. Dc in 4th ch from hook. *Dc in next 7 sts. Skip next 2 sts, dc in next 7 sts. (dc, ch 1, dc)* Repeat until last st, where you will do 2 dc in last st.
3. Ch 3 (counts as a dc). Dc in first st. *Dc in next 7 sts, skip 2 sts, dc in next 7 sts, (dc, ch 1, dc) in next st (which will be the ch 1 sp)* Repeat until last st where you will do 2 dc in last st (which is the ch 3 from the previous row).
Optional: Repeat step three two more times, then switch to color B. Repeat step three, switching colors every four rows (or as desired), until piece measures about 20 - 22 inches long. Sew in ends and fold over to desired shape (I made mine look like a foldover clutch, you may prefer something more bag like) and stitch together sides.
Look stylish as hell.