And don't forget Google Wave that did the whole "chat integrated with various multimedia elements" decade before the competition (and arguably, better, coz those could be interactive elements not previews of websites and embedded media)
For me, Wave was the most exciting thing Google ever tried. The requirements exceeded most corporate hardware, but the whole "email as a wiki page" struck me as the future. Replay the messages in order to follow the responses.
(there was a lot of other stuff going on in there too)
