You'll notice that some of my posters are upside down. Well, the holes do inevitably tear, so sometimes I flip them and re-punch. It's actually easier to look through the posters when the titles are down there! The other option are these gadgets that look like single hole punchers, but actually stick a thin plastic ring around a hole that's already been punched. VERY useful for this purpose. I wouldn't use them on all loose leaf paper, but for posters it's worth it.
Anyone else have tips on organizing their posters?