Sublime Text 2 - On the download page, all available versions are shown, with the OS you’re running preceded by a black dot instead of a white one.
Amazon - After completing your order, the page title changes to: “Amazon.com Thanks You”
/via Steven Scarborough
Tehula - The slideshow demo uses names of characters from Lost.
OS X Mountain Lion - When you trigger the Speech & Dictation dialogue, the fans on your machine immediately go minimum speed to prevent background noise.
Facebook - When you have your relatives marked on Facebook, you can search for them by their relation to you.
/via Ian Arthur Spaeth
Twitter - When submitting the same tweet twice, an error message is shown.
/via Sindre Sorhus
Mixpanel - When changing your password, the field for the current password has an old style key, and the new password has a modern key.
/via Timothée Boucher
Make me a Cocktail - If you click on the search button with nothing in the search box, it types out a random cocktail for you to try.
/via Nick Wilkins
iCal - Shows birthdays from Address Book with the person’s name and age.
/via Clemens Mayer