Add multiple items to cart
One way of doing it is by using the Views Bulk Operations module. There is a patch which has recently been committed and offers the "Add to cart" action over here: http://drupal.org/node/1553700

Once your view is built (fields only) you can add a Content VBO field and choose the Add to cart action from there. In theory, redirection to the cart can be done by including the ?destination=cart parameter when calling the View which should be honored once the form is submitted. However, at the moment this appears to only add one item and redirecting rather than all items that have been selected.