Amazon currently has the Samsung Galaxy S8 available, unlocked, for just $599. That's a great price for a brand new, unlocked device that will still be one of the best smartphones on the market when the Galaxy S9 launches later this month.
This is an unlocked Galaxy S8, but it does not support CDMA networks. So it'll work on T-Mobile and AT&T here in the US, but not Verizon and Sprint. Otherwise, this is the same Galaxy S8 that is sold by the carriers. It sports that 5.8-inch display, along with the Qualcomm Snapdragon 835 chipset inside, with 4GB of RAM and 64GB of internal storage. There is also a micro SD card slot available for expanding storage, should you need it. All of it is powered by a 3000mAh battery. Now it is still running on Android Nougat, but Android Oreo is currently in beta for the Galaxy S8, so it should be rolling out shortly.
This item is also eligible for Amazon Prime's free shipping. Which includes free two-day shipping, and pretty cheap (usually $3.99) next-day shipping if you need it extra fast. If you are not an Amazon Prime member yet, you can sign up for a free trial of Amazon Prime. You'll get 30 days free (if you're a student, you get 6 months), and then it's $99/year (or $49/year for students). Prime members do get a whole lot more than just free shipping though, so be sure to check out the full benefits.