The unlocked, unsubsidized phone goes for $399 and is compatible with AT&T, T-Mobile and other GSM service providers. This one won't work on Verizon or Sprint.
The Nexus runs Android 4.0 (Ice Cream Sandwich). All the specs on the phone are the same as the ones sold with contracts.
So far, this is the only offering under the "Shop Devices" tab of Google Play, the media hub where consumers can get music, apps, movies and books.