Bit of a no brainer, I know, but if you haven't already, make an animated version of all your ads. I hadn't used flash for years and was putting this off for months. I hate relearning software. So a couple of days ago I downloaded a cracked version of banner designer pro from TPB. It was so ridiculously easy to use I was pumping out a new .swf banner every ten minutes. 3 or 4 days later and my CTR has pretty much doubled. You'll need to leave your old static ads there too as not all sites accept flash ads.