Google has a bunch of Nexus 5 cases listed, but not available

Along with the Nexus 5, which is finally up for sale, there are four different bumper cases - black, grey, bright red, and bright yellow - as well as two "LG Quick Covers" in black and white. The bumper case has a hard outer shell and rubber liner that will help to absorb shock if you happen to drop your new device. The LG Quick Cover and combines a case for the back with a flip-cover on the front which will work just like an iPad Smart Cover, or Nexus 10 cover, and allow you to unlock your device just by opening the cover. 

Both the bumper and the Quick Cover will be compatible with "Nexus Wireless Chargers" (which makes it sound like the Nexus 5 will work with the wireless charging orb as well as the new charging pad). As you might expect, the pricing is a bit absurd with the bumper case costing $34.99 and the Quick Cover clocking in at $49.99. Of course, you can't actually buy any right now; they are all listed as "coming soon".

source: Google Play (Bumper Case & Quick Cover)