Callisto is about improving the productivity of developers working on top of Eclipse projects by providing a more transparent and predictable development cycle. It is the simultaneous release of 10 major Eclipse projects at the same time.
http://www.eclipse.org/callisto/

1. Platform
      www.eclipse.org/platform
      Java Development Tools (JDT), User Interface/Core Tooling, Plug-in Development Environment (PDE).
2. C/C++ Development Tools (CDT)
      www.eclipse.org/cdt
      Bring a fully functional C/C++ development environment to the Eclipse platform.
3. Business Intelligence and Reporting Tools (BIRT)
      www.eclipse.org/birt      
      A reporting system.
4. Data Tools Platform (DTP)
      www.eclipse.org/dtp
      Provides data management frameworks and tools.
5. Eclipse Modeling Framework (EMF)
      www.eclipse.org/emf
      A modeling framework and code generation tool for building tools and other applications based on a structured model.
6. Graphical Editing Framework (GEF)
      www.eclipse.org/gef
      A framework that extends the Model-View-Controller paradigm to graphical editors.
7. Graphical Modeling Framework (GMF)
      www.eclipse.org/gmf
      Bridge EMF and GEF to allow for the generation of graphical editors.
8. Test and Performance Tools Platform (TPTP)
      www.eclipse.org/tptp
      Supplying frameworks and services to build unique test and performance tools.
9. WebTools Platform (WTP)
      www.eclipse.org/webtools
      Extending the tools for developing J2EE web applications.
10. Visual Editor Project (VE)
       www.eclipse.org/ve
      Supplying frameworks to create GUI builders.

Source from http://eclipse.sys-con.com and http://www.eclipse.org/callisto/