[ic] shipping issue - how to not charge shipping?

[interchange-users@interchange.redhat.com (Mark Lehrer)]

Hello.

We have had our cart working for awhile now.  However, we are trying
to sell items (e.g. maintenance agreements) that do not require
anything to be shipped; although the customer could combine one of
these agreements with a product box, and therefore would need a
shipping charge.

How can I configure this?  I have been checking out the archives
and online documentation but haven't seen this issue (yet).

Thanks,
Mark Lehrer