Write "ongoing research projects" in a CV What is a neat way to include "ongoing research projects" in a mathematician's academic CV?

By this, I mean something that is narrower than a generic "research interest", but not quite as defined as a "paper in preparation". 

One colleague of mine uses the following notation:


  Cubic Nonlinear Schrödinger Equation
  
  main objectives: study of such and such properties; 
  
  in collaboration with Dr. X and Dr. Y
It's not a standard practice to list "ongoing research projects" (from which you don't yet have any papers) on your CV.  I wouldn't even say it's standard to list papers that are "in preparation" (some people do, some don't; I personally am not a fan of this).

The point of a CV is to give a summary of your academic history, accomplishments and experience.  It's not a place for people to get to know your hopes and dreams.  And I think it will look strange on an academic CV, so I would recommend against including listing ongoing projects.

If you're asking about this in the context of job applications/promotion/etc, the place to write about this is in a research statement (and possibly a cover letter if you think it's really relevant).  If you're asking about this in the context of grants, the place to discuss this, if it's relevant, is in your proposal.

Two things you can do, if you really want to, is have a line about "research interests" and have a section listing collaborators.  (On a related note, some people also group papers by research topic, making research interests clear, though I personally don't like this in most contexts.)  These aren't typical, but they won't look so strange to make people think you are weird for including them.