Create a view function inside your app:
from django.contrib.auth import views as auth_views
...
def login_user(request, template_name='registration/login.html', extra_context=None):
response = auth_views.login(request, template_name)
if request.POST.has_key('remember_me'):
request.session.set_expiry(1209600) # 2 weeks
This view practically calls Django's original login view function, and then checks if the request contains a "remember_me" field checked. Also, in the settings file, you should make sure to set SESSION_EXPIRE_AT_BROWSER_CLOSE = True to make the default behavior such that the cookie expires when the user closes the browser.
You should now edit your login template to add the checkbox to the login form:
...
<input type="checkbox" name="remember_me" value="true">Remember Me</input>
...
Last, you should hook you application url to the new login view we just defined. Edit you applications urls.py:
urlpatterns = patterns('',
...
url(r'^login/$', login_user, {'template_name': 'registration/login.html'}, name='auth_login'),