You won’t see Twitter, Slacker or Facebook, among others, on this list. Although I find them indispensable, the services aren’t unique to a mobile phone. To make my Top 10, an app must deliver an experience you couldn’t find on your computer — something, in other words, that exemplifies the smartphone at its best.
Instapaper didn’t make the Top 10 but got an honorable mention in the final paragraph. Thanks!