I basically just wanted a lightly padded laptop cover that added a little peace-of-mind protection but not a lot of bulk. I cut 14'' x 10'' rectangles for the exterior and lining. I got those measurements because my laptop is 13x9, and I figured an inch would be enough for a seam allowance and a bit of wiggle room to accommodate the thickness of the laptop (which is less than half an inch).
I used purple metal jacket zipper from the SAS zipper bin and applied it as an exposed zip, using a tutorial from DIY Style Vodcasts. I skipped the stabilizer because my fabric wasn't stretchy, but I did like their idea of taping it down instead of pinning, and that worked very well.
I tried to get clean edges on the inside by ironing a little hem in before stitching the fabric pieces to the zipper on the inside. This more or less worked. You can see the white and black from the exterior fabric peak out from under the purple inside, but at least none of the edges are raw. Not the very best option, but passable.
I used a heavyweight fusible interfacing on the exterior pieces and sandwhiched two cuts of a fleece-like fabric between the exterior and lining as the padding. The padding fabric was labeled as a fleece, but it wasn't thick like most of what you see at Joanns; it was more like felt in thickness, but was softer like fleece.
I decided half-way through to add a patch pocket to the top for the laptop charger, phone charger, little post-its, etc. I didn't really measure it, but the size worked out just about right. I sewed a rectangular scrap of the lining fabric right sides pressed together, turned, and applied it as a patch pocket. I gave the pocket a nice deep pleat in the center for roominess, and a button-closed top flap to hold it all in. My topstitching could have been neater, thats for sure, but I can live with it. The button is from my stash, probably from JoAnns.
Overall, I'm very happy with my laptop cover. It fits perfectly, has a good amount of protection but not bulk, and I learned a bit about zipper application in the process. And after a full day of traveling (Phoenix to Toronto, Toronto to Zurich) I can say that my laptop was not damaged or scratched one bit. And it fit into the seatback pocket with my magazines, which was convenient.
It's a bit after 6pm here in Zurich. I had a really nice day walking all around town with my Aunt. I stumbled into a yarn store owned by a hilarious British woman. Her and I talked for some time. She told me about two fabric stores in town that I'll be visiting soon. She also talked me into buying some super-soft, Swiss-made baby alpaca fiber yarn. Darn :)