gistfile1.pyw

# ---- some file that is processed early in Django's execution (like a urls.py or __init__.py file)

from product.models import ProductManager

def deal_o_day(self):
    """Determines which product is the current Deal of the Day"""

    return self.filter(stuff_in_stock__gt=0, foo=bar)

ProductManager.deal_o_day = deal_o_day

# ---- middleware.py

from django.http import HttpResponseRedirect
from product.models import Product

class DealODayMiddleware(object):

    def process_request(self, request):
        """Redirects users to the product detail page for the deal of the day when they access the site root"""

        if request.path == '/':
            product = Product.objects.deal_o_day()
            return HttpResponseRedirect(product.get_absolute_url())