Which iPhone apps do you like?

So, I finally joined the 21st century and got an iPhone. Until now, I had been rocking an old-school flip phone, which most people assumed was a toy for Toby. But then I lost the battery, and when I tried to replace it, Verizon told me they didn't make it anymore. I was like, OK, I get it.

Now I'm excited to have a shiny new iPhone. My only question is: What apps are awesome? I know nothing about iPhone apps--except Hipstamatic--so I'd love to hear your recommendations! Which apps do you use? I'm clueless!

P.S. Me with my old phone: