For those of you with an iPhone of an iTouch, it seems that both American and Delta are offering the possibility of winning one million miles through their new iPhone applications.
For American, you need to register within the app after downloading it, details can be found here: http://fly.aa.com/index.aspx
For Delta, all you need to do is log in with your SkyMiles number in order to get your entry chance. The Delta Details are here: https://www.delta.com/traveling_checkin/travel_tips/mobile/iphone/index.jsp
Aside from the possibility of free miles (which is always a good reason) these apps also allow flight searching, booking, flight status, mobile check in and other features that could be useful if you use an iPhone for everything.