Project Spark is a technology preview of a simplified 3D building information modeling (BIM) solution. Using Project Spark, building professionals can create designs efficiently with real-world building objects, produce more reliable documentation faster, and share files (not with the preview product) with consultants using Revit or AutoCAD-based products.
Project Spark is based on the Revit Architecture code base, but does not support conceptual design, analysis, rendering, advanced collaboration, and API.
Try this Revit product for free for almost a year. The technology preview will operate until July 7, 2012.
Project Spark supports linking models created in Autodesk Revit Architecture 2012, Autodesk Revit MEP 2012 and Autodesk Revit Structure 2012 but the supported applications cannot actually open models created in Project Spark. Project Spark cannot open Revit 2012 files.
More information is available on the Project Spark Wiki page
Time will tell if there might be a future Autodesk Revit LT 2013 or maybe Autodesk Revit Architecture LT 2013.