Light Saber Unleashed. Free. Uses the accelerometer to do light saber sound effects when you wield your phone in sword battle.
Ghostly Discovery. Free. Ghostly International music app. Very cool interface. Tune your internet radio by mood + speed + more or less electronic.
Elementary Math. 99 cents. Good electronic flashcards plus a cool "math wheel" interface. I got this for Vigo.
Camera Bag. $1.99 Add filters to your photos to make them awesome instead of kinda crappy.
Check out the Camera Bag Flickr Pool to see how nice it is.
Nearby. Free. This is the app that Platial built. I haven't used it since we left the US because of not having unlimited data, so I don't know how good it is in Europe. Try the "collections" tab, it's my favorite.
Shazam. Free. Identifies songs. Very simple, and totally cool.
Skype Free. You can use your wifi to make cheap calls when you're at home and save phone minutes. I have a 2-euro per month subscription for calling US phones.
Urbanspoon. Free. Not sure if it works in Europe, but in the US it is the coolest restaurant finder ever.
Leaf Trombone and Ocarina. 99 cents each. Wind instruments. Seriously awesome.
Read it Later. Free or paid version for more features. Read it Later is my current favorite tech thing. It's an iPhone app that goes with a free Firefox plug in. install the plug in and any time you open up a great but long blog post or article that you don't have time to read, click on the checkmark in the toolbar and close the window. Then your phone app will sync with the browser plug in and pull in the webpages for you to read offline while you're in line at the post office. Brilliant!
Radio Lab. Amazing show. My ultra favorite. Asking the big questions. Science-heavy, but not daunting. Best show so far, about Memory and Forgetting. Blew my mind.
The Moth. True stories told onstage without notes.
Rocketboom. Tech and internet stuff.
TED Talks. Inspiring amazing projects, 20 minute talks.
This American Life. Stories on a theme.