Hmm... If I've been really, really bored I usually end up with my arse on one chair, my back resting againt the corner between backrest and armrest, one leg on my table the other one resting on another chair and my other armrest.
I'm not sure you'll be able to imagine this... It's a really weird way of sitting were I don't get a lot of blood to the brain, so it doesn't help me at all, but it's a bit comfy.
I am however always dizzy when I stand up after that.