For carriers, you can target various telcos in the U.S. and Canada. In the U.S., you can target Verizon, Spring, Nextel, T-mobile, AT&T, Metro PCS and Cricket. In Canada, you can target Rogers, Telus, and Bell Canada.
If you're advertising a mobile application, your ad will only appear on devices that can download those apps. Additionally, the link in the ad will allow users to download directly. Just add your app name to the end of either itunes.apple.com or market.android.com and it will automatically feature anchor text directing users to download the app.
