Aside from the extremely obvious... instagram, twitter, bloglovin', blogger, facebook...
1. Afterlight - you've probably seen a million bloggers suggest this, and I know that can make me skeptical, but honestly this is so worth the 79p! I actually prefer to edit photos on this if they were taken on my phone rather than upload them to the computer to edit.
(I mentioned it in my last post). It's a game, it's free. You basically build up your camp, collecting elixir and gold battling goblins and other clans. I'm not sure if there are higher aims than that, there probably are, but I don't know them yet 'cos it's still early days!
Do you use any of these apps? Are you as reliant on some apps as I am? I think it's great that I can carry around a calender in my pocket! And I don't have to even think about tweeting if I'm busy! And I love a good war game.