This one can be a real game changer/time saver. Imagine getting everyone on the same site without having to wait for everyone to type in a URL. No waiting to see if everyone got it right or is on the right site. Think of it as an audio QR code.
Heard about this one at the Google Ed Camp, tried it out at the 2nd 6th grade 1:1 session this summer, and it is a hands-down winner extension that is free on the web-store.