Sadly, I believe the best you can do in Excel is send out a template
with the standard charts in it, then instruct all the recipients in how
to save those as user-defined chart types in their own Excel setup. It's
a strange failing on the part of Microsoft, to have failed to provide a
way of distributing user-defined chart types around an organisation.

It might be possible to send out the file in which the user-defined
charts are stored, and instruct people in how to install it in the
appropriate location, but that will end up replacing whatever
personalised file they themselves have created, and many people may be
unhappy with that.

I KNOW HOW TO DO THIS!!
Finally I can help somebody out after getting help from this forum as a
lurker for years.

OK, the file that gets created/populated with the user-defined charts is
called XLUSRGAL.xls .

You will have to copy this file to the correct location in Documents and
Settings on each individual system in order for the users to have access to
your chart templates.  Here's my path  C:\Documents and
Settings\"username"\Application Data\Microsoft\Excel  

Obviously "username" is what you replace with each user's name.  I've shared
and modified user-defined charts and successfully shared them between 3
systems this way.

props to Chip who originally discovered this one,
A