The Lab will be out in a couple of months and it sounds like a blast.
The Lab is set in the Portal universe, in a lab at Aperture science. It's a collection of 12 VR demos for the HTC Vive, but that description is pretty dry compared to what it actually offers.
A central hub room contains collectibles you can bring back from the world you visit, which you can access by grabbing one of the spheres that act as portals and pulling them towards you.
Some of the experiences are referred to as "postcards" by Valve according to cnet, and recreate real places in a VR world by piecing together a collection of digital images.
As well as a physics-based catapult game, and a chance to fend off stick enemies with a bow and arrow, there's also a bite-sized, bullet-hell arcade shooter controlled by holding the spacecraft in your hand and having it dodge incoming fire.
The Lab will release shortly after the HTC Vive's debut on April 5, and it'll be totally free.