This is actually a bag I made as an added bonus for my eBay auction of an OLPC laptop. I liked the result a lot, so I've made another one for myself and thought other OLPC owners might like it.
It's basic, stylish black.
It has adjustable straps with easy-release parachute buckles - so it can be worn as a backpack, messenger bag or carried like a briefcase.
It's weather proof. I hesitate to say 'waterproof' because I haven't tested that, but it is made of a waterproof lined canvas and the closure is of a double fold design that is intended to keep the elements out.
It form-fits the laptop with just enough give that it can fit in either way up.
Possibly unique closure system. It has a side opening so that you can remove the laptop without taking it off; you just reach behind and unsnap it and pull the laptop out by it's handle. All the the closing snaps are between the bag and your body so that no one else can open the bag without you knowing.
It sits naturally in the small of your back, the idea being that the slight curve of your back leaves a space big enough for a thin bag like this. You could even, if you wanted, wear it under a jacket sort of like a laptop shoulder holster. That's actually not a bad analogy; it's possible to pull the laptop out in about 2 seconds.
The design is originally something I thought of for carrying a hardback book without bothering with a big obtrusive bag.
Step 1: First Find Your Materials.
Anyway, here's something that is heavy and black: I believe it is called Limonto. It seems to be two layers of canvas laminated with a membrane of rubber. For 1 bag, 1 yard will be plenty.
Buckles, or something that can join reasonably heavy straps and be adjustable. I got silver parachute buckles which are way better than what I was looking for - some of those backpack strap toggles.
Snaps. You can get these from a craft store along with a tool for attaching them.
Step 2: Cut and Make a Tube
The basic design of the bag itself is a tube that is then closed at one end. For that you need a rectangle as below where x is 2 or 3 inches bigger than the circumference of the laptop and y is maybe 6 inches longer than the laptop.
You also need straps from the material. They need to be strips that are just over twice the width of the buckles. They also need to be as long as you can make them to maximize your options. Allow for these later when you cut the rectangle
As in the diagram, fold the rectangle to halve the x length - by wrapping it round the laptop. Sew along the y edge to make a tube - sew line o (at this point the bag is inside out). You should end up with a tube that is reasonable snug if you slide the laptop into it - but not too snug.
As in the last two steps of the diagram, roll the tube so that the join is in the middle and fold the two flaps of it over. Then sew through both of these to the side of the tube to keep the flaps flat with the tube - sew line a. Take a look at your pants leg; chances are at least one side is sewed like this.
Step 3: Make the Straps
Each piece of strap is made of a strip of fabric that is just over twice the width of the final strap. You fold the edges into the middle, and they should overlap a little for neatness. As in the diagram, you sew a single line thread down each side at "b". This is tricky sewing to get looking good because you see every stitch. I got good results using a binder clip for the first side to make sure it was folded right.
For the second side I used a bag buckle - which coincidentally was the right width, the buckle you get may be fine for this. By letting the machine pull the fabric through, it folded itself over in the buckle to exactly the right width. In that way all I needed to think about was keeping the stitches the same distance from the edge.
Finally run the whole thing through again with a zigzag stich at "c" to keep the join all contained.
Step 4: Attach the Straps
The diagram is not quite to scale, but you may be able to see from the pictures. The laptop sits in one end and the other will fold over to close. You need to allow for enough space to close the bag at the one end - about a half inch - and then place the straps at balanced points based on where the laptop will be.
The easiest way to do that is put the laptop in and pinch the edge a half inch to get it in the right place, the stitching on the tube will be between the straps. Lay the straps on and mark where they will be. A good strong join is to sew a box with an X in it.
Also, and this is very important, the bag will sit on your back with the strap side against your back and the opening will be on your right side (if you are right-handed). So on the diagram, the right side is the top of the bag.
In the pictures, the straps on the left side, are those that go upward.
Step 5: Finishing
The method I'd originally planned for the snaps was to have the end fold over flat a couple of times. The idea is that the folding seals the end up to moisture.
Once I actually started to fold it around the laptop, I changed that so that the corners would fold in and snap and then would fold over again into the center. That holds it closed well with a single center snap, but the original method would probably work well too.
Basically just stick the laptop in the bag and fold and mark where the snaps seem best to you.
I also added a spare bit of strap to close in the center, which makes opening and closing a lot easier.
Step 6: Press and Wear
Here are some pictures where I attempted to show the process of getting the laptop out, because I think this is one of the strongest elements of the bag.
With the bag on, the closed snaps are against your back, so noone else can reach them. Opening it, if you imagine your hand slides underneath so that the back of your hand is against your back. In that position, it is easy to grab the snaps and unpop them.
Then you reach into the bag and pull it out to the side. The bag is snug enough that the laptop is not going to just fall out, but it should slide easily out. Sliding the laptop back in requires some more coordination, but can still be done pretty quickly.
This is my first instructable, hope you liked it. Feedback appreciated!