Six Gmail Labs have graduated and are now features of Gmail

1. Search Autocomplete - Gmail will suggest terms to help you find your
item more quickly.
2. Go To Label - If you have keyboard shortcuts enabled, typing in the
search box will autocomplete and suggest a label name.
3. Forgotten Attachment Detector - Gmail looks for phrases in your email
that suggest you meant to attach a file and alerts you if it looks like you
forgot an attachment.
4. YouTube Previews - If you receive a message with a YouTube link in it,
you can now watch the video right below the message.