MVC :: Create Views That Perform Multiple Tasks?

This is my first forray into ASP.NET MVC, having been doing WebForms for nearly 6 years now. I've read through various tutorials and guides on getting started with MVC, but I've a few questions about how you're meant to do things:

UserControls for entities

In an application I wrote a few years ago (using WebForms) there were many entities that had an associated postal address (which existed as an instance of an Address class), so I created a UserControl that contained fields for working with addresses. During the page lifecycle I would pass the business object's .Address property to the UserControl for display and for population upon a successful and valid postback. How would I do something like this in MVC? My current project has a similar situation where common sets of fields are repeated throughout the application and all 'map' to the same class.

Modifying the page/view on 'postback'

Say I'm working on a data-entry form for an online B2B ordering system, where the user manually enters order items into a series of textboxes arranged in a table. The system can only provide so-many textboxes at a time (usually 5 or 10). If the user ran out of textboxes they would click an "Add more rows" button that performed a postback that was caught by that button's server-side .Click event handler. The page's class would then add more rows to the page; ASP.NET's stateful nature made this easy to implement. But in MVC there is no ViewState and I haven't found much information about how you'd do this, or anything like this. All of the tutorials and guides assume a form posting is only for data submission.

Multiple tasks per page/form

In a similar vein to the above, how do you create views that perform multiple tasks? In my above example I cited a webform that had two buttons: one to submit the form for actual processing, and another button that just modified the page (by adding more data-entry rows).Given that Controllers' actions are bound to URIs rather than what combination of fields were submitted, does this mean that I would have to interpret the posted data myself and branch based on that?

Componentised self-contained controls (e.g. sidebar forms)

Finally, in many web applications you have the main form in the middle, but also things on the periphary of the page (e.g. a sidebar) that might have their own logic. For example, in one WebForms application I wrote last year there was a 'Quick contact' form in a UserControl located elsewhere on the page. When the user clicked the form's button the UserControl's logic handled the postback details independently of the page containing the UserControl (but there was only one <form> element in the whole rendered page). The user was returned to the page they clicked the button on, with everything in identical state as to how it was before, exccept for the UserControl which reported that the email was sent. Again, MVC's stateless nature would make something like this hard to implement, unless there are some techniques not covered in the tutorials?