Basic MVT issue in Django
Context processors and RequestContext (see Tyler's answer) are the way to go for data that is used on every page load.  For data that you may need on various views, but not all (especially data that isn't really related to the primary purpose of the view, but appears in something like a navigation sidebar), it often makes most sense to define a custom template tag for retrieving the data.
I have a Django website as follows:

site has several views
each view has its own template to show its data
each template extends a base template
base template is the base of the site, has all the JS/CSS and the basic layout

So up until now it's all good. So now we have the master head of the site (which exists in the base template), and it is common to all the views.
But now I want to make it dynamic, and add some dynamic data to it. On which view do I do this? All my views are basically render_to_response('viewtemplate.html', someContext). So how do add a common view to a base template?
Obviously I will not duplicate the common code to each separate view...
I think I'm missing something fundamental in the MVT basis of Django.