Let me first say that skydiving wasn't the only exciting thing happening here, but watch the video anyway.
Now, the non-extreme-sport stuff.
The improvements to Android with Jelly Bean had everyone talking. Project Butter, improving responsiveness for a smoother interface is very noticeable. Attendees were given a Galaxy Nexus and Nexus 7 tablet, both with the new Jellybean OS so we could see for ourselves.
Incidentally, ZDNet featured a picture of GDG organizers Aygul and Misha posting with the new Android Jellybean statue. These two were married a year ago and spent part of their honeymoon at I/O 2011. Happy one year anniversary, guys!
Google+ Invites! With Party Mode! It was a big hit at the after hours event, as you can see.
Like any new technology, however, there are a few initial kinks to work out, as Will Wheaton discovered. Don't worry, it's a great app and is going to vastly improve your social life :)
Google Compute Engine launched, with an amazing demo, showing a live genome analysis using 10,000 and 600,000 CPU cores. That's some computational power.
What else? Google Docs offline, Chrome for Android and iOS, offline maps for Android, a new Google Drive SDK, a new Maps API, and Google Now. These are just a few highlights. Everything is available online. The session on the future of GWT was very popular, with a long line to get in. There's no way to see it all as an attendee, so most of us will be watching sessions when we get back home.