All the form controls can be used anywhere where phrasing content is expected, which means they can appear just about anywhere in the body of the document. If you don’t need to have them submitted back to a server then there’s no need for them to be associated with a form, however I’ve noticed that in some browsers you can’t take advantage of the form validation features unless the elements can potentially be submitted.
One feature new to HTML5 is that form controls no longer need to be the direct child of a form element in order to be submitted with that form, the form attribute allows you to specify the id of the form the element should be submitted with.