storing a bunch of models in a session before submitting to database

How is this usually done? What I'm trying to do is kind of like a
shopping cart, except I need to hold more than just one model.

Say for example you want to assign tasks to people, but you want to be
able to pick either the person first, and then assign tasks to him, and
then submit the both things together to the database, or be able to set
up a bunch of tasks first and then assign them all to one person, and
then submit.

I think I want to have a page that diplays the tasks and person and a
some forms that redirect back to the same page after they add something.