At the moment I have a Kensington laptop stand. Its great, does the trick folds flat and I take it with me if I'm working elsewhere, and use it on my desk when I'm here. But it weighs 688g:
I have a backpack for my laptop (I had a shoulder bag for about a week but I ended up with my whole skeleton mis-aligned), which I use when I'm travelling and in London that means a lot of walking and usually in heels - so weight is a real issue for these trips. I really like my back the way it is - healthy! I weighed the cardboard one for comparison, and tried my laptop on it.
No contest, certainly for when I'm on the road :) OK so it will probably go soft or get wet or something, but for £7.50, I think I can probably afford to replace it. All I need now is some decoration ... stickers, perhaps?