We currently have four 125x125px ad banner spots available on iPhone/Apple Blog with over 480,000 Est. Impressions a month. The majority of this traffic comes from the US, with the UK and Canada making up the majority of the rest. You can find more details and purchase the ad below: http://buysellads.com/buy/detail/63487
It's difficult to say how much impressions we get from US. However, if we look at analytics of last 30 days, we drive huge traffic(52.24%) from US alone.
Yes. 300x250 ad slot is available below post and besides Recent Posts. It will offer best visibility for your banner.