If you were lucky enough to get into the Google I/O conference before it sold out, you will have a nice email in your inbox that says Google wants to ship you a free Nexus One before the show.
Last year they gave developers a Google Ion -- basically a Magic, but they waited until the opening keynote to distribute them. This year is different because they decided to give developers a Nexus One early so developers have them activated and ready to go without wasting time during the show.
I'm sure there are either 1) a lot of happy developers right now because they got a free phone, or 2) a lot of pissed off developers because they already shelled out $500 when the phone was first launched.
Update: It sounds like developers attending from the United States are receiving a Motorola Droid -- the Nexus One is only for International attendees.