The unlocked Samsung Galaxy nexus is now available for a decently priced $399 on the Google Play Store. That means you will be purchasing directly from Google for compatibility with over 200 GSM/HSPA+ carriers worldwide, including AT&T and T-Mobile. The price is also free from any contracts, in case you were wondering. Unfortunately, it looks like only those in the US can purchase the Android 4.0 Ice Cream Sandwich-powered handset from the Play Store at this time.
Source: Google Play