Feather iOS App - The Twitter bird turns slowly green as you type and goes red when you get to the 140 character limit.
/via Anna PS
Path - If you forgot to add one of the three requirements while uploading a photo on Path for iPhone, the buttons bounce as you tap on Save.
iOS - When you enable airplane mode on iPhone, a little airplane icon flies from the edge of the screen.
Calculator App - When you rotate your iPod, the app uses the screen real-estate to add functions.
Delivery Status app - It detects if you have a tracking number on the clipboard on launch, and it also says from which courier.
/via Patrick Patience
iOS - Mail inbox automaticly scrolls to the top when you receive a new email, unless you have already scrolled down through more than 3 emails.
Offcial Twitter app for iPhone - Dragging down the whitespace of reply screen shows what tweet you are about to send reply.
iPhone - Turn shift blue via double click and continue in capslock.
/via Katrin Friedmann
Reeder app - website makes use of some nice CSS3 transitions.