Typinator - Menubar icon dims when you activate password / security form fields.
Typekit - Tiny little arrows next to input field for numbers.
Apple - Signup form shows a lighter version of input description once you clicked on. Then once deselected the blue border subtly fades out.
Github - Credit card autodetection by number
Tumblr - while creating new blog the form field is already filled in and your entry aligns to the right of the form