Avoid the flooring, at least the laminate 'wood' flooring. I'm speaking from experience. Not only is that stuff super-toxic to cut, it turns out that it can't bend - it just shatters. I thought that being 'strong' and 'resilient' meant that it wouldn't break from the mere stress of being bent 50% of it's length.
But seriously, if you want to make an UBERBOW I have some ideas that are pretty silly, but may work. I heard some people talking about making 'steel' bows from pickup truck leaf springs. You could also do a sort of 'stick' bundle with those driveway markers lashed together. If you want to be truly ridiculous and go nuts, involve duct tape. EVERYTHING is better with duct tape.
One thing, all kidding aside this time, that looks promising is the vinyl trim and moulding. It's perfectly shaped, easy to work, comes in long lengths, and bends easily at the same time as being strong. If you were to use this as a backing to some harder material, such as PVC or even the oak boards they sell, I bet you could make something fairly strong and durable.
Of course, like they all said, it's not exactly the right board for these 'new fangled' hippy-bow modern ideas. Pretty soon you'll be talking about putting wheels on your bow and ignite some kind of firestorm free-for-all. For shame.