I'm currently planning out the UI improvements for HelpSpot v2 and while I have a bunch that are on the list I'm always looking for good ideas. There's so much out there about good website design and UI but almost nothing about web application UI. I think people think website UI is the same thing as web application UI, but those people be wrong! So have you used any apps which are really spiffy lately? A specific UI element that really wow'd you. Note that I'm looking for elements that are practical not just "cool".