A new cloud-based offering for team collaboration launches on May 1. It's called Project Lite, and you'll find more details here on the Microsoft website.
Apparently Project Lite is used in conjunction with Project Online.
The range of Project-related products and services from Microsoft is growing. Here is some helpful guidance on sorting out what's what (hopefully it will be updated soon to include Prject Lite).
If you are a Project Lite early adaptor, share your experiences via a comment below.