Index: django/contrib/sites/managers.py
===================================================================
--- django/contrib/sites/managers.py	(revision 13303)
+++ django/contrib/sites/managers.py	(working copy)
@@ -4,17 +4,38 @@
 
 class CurrentSiteManager(models.Manager):
     "Use this to limit objects to those associated with the current site."
-    def __init__(self, field_name='site'):
+    def __init__(self, field_name=None):
         super(CurrentSiteManager, self).__init__()
         self.__field_name = field_name
         self.__is_validated = False
-
+        
+    def _validate_field_name(self):
+        field_names = self.model._meta.get_all_field_names()
+        
+        # If a custom name is provided, make sure the field exists on the model
+        if self.__field_name is not None and self.__field_name not in field_names:
+            raise ValueError("%s couldn't find a field named %s in %s." % \
+                (self.__class__.__name__, self.__field_name, self.model._meta.object_name))
+        
+        # Otherwise, see if there is a field called either 'site' or 'sites'
+        else:
+            for potential_name in ['site', 'sites']:
+                if potential_name in field_names:
+                    self.__field_name = potential_name
+                    self.__is_validated = True
+                    break
+        
+        # Now do a type check on the field (FK or M2M only)
+        try:
+            field = self.model._meta.get_field(self.__field_name)
+            if not isinstance(field, (models.ForeignKey, models.ManyToManyField)):
+                raise TypeError("%s must be a ForeignKey or ManyToManyField." %self.__field_name)
+        except FieldDoesNotExist:
+            raise ValueError("%s couldn't find a field named %s in %s." % \
+                    (self.__class__.__name__, self.__field_name, self.model._meta.object_name))
+        self.__is_validated = True
+    
     def get_query_set(self):
         if not self.__is_validated:
-            try:
-                self.model._meta.get_field(self.__field_name)
-            except FieldDoesNotExist:
-                raise ValueError("%s couldn't find a field named %s in %s." % \
-                    (self.__class__.__name__, self.__field_name, self.model._meta.object_name))
-            self.__is_validated = True
+            self._validate_field_name()
         return super(CurrentSiteManager, self).get_query_set().filter(**{self.__field_name + '__id__exact': settings.SITE_ID})
Index: tests/regressiontests/sites_framework/__init__.py
===================================================================
Index: tests/regressiontests/sites_framework/models.py
===================================================================
--- tests/regressiontests/sites_framework/models.py	(revision 0)
+++ tests/regressiontests/sites_framework/models.py	(revision 0)
@@ -0,0 +1,36 @@
+from django.contrib.sites.managers import CurrentSiteManager
+from django.contrib.sites.models import Site
+from django.db import models
+
+class AbstractArticle(models.Model):
+    title = models.CharField(max_length=50)
+    
+    objects = models.Manager()
+    on_site = CurrentSiteManager()
+    
+    class Meta:
+        abstract = True
+    
+    def __unicode__(self):
+        return self.title
+
+class SyndicatedArticle(AbstractArticle):
+    sites = models.ManyToManyField(Site)
+
+class ExclusiveArticle(AbstractArticle):
+    site = models.ForeignKey(Site)
+    
+class CustomArticle(AbstractArticle):
+    places_this_article_should_appear = models.ForeignKey(Site)
+    
+    objects = models.Manager()
+    on_site = CurrentSiteManager("places_this_article_should_appear")
+
+class InvalidArticle(AbstractArticle):
+    site = models.ForeignKey(Site)
+    
+    objects = models.Manager()
+    on_site = CurrentSiteManager("places_this_article_should_appear")
+
+class ConfusedArticle(AbstractArticle):
+    site = models.IntegerField()
Index: tests/regressiontests/sites_framework/tests.py
===================================================================
--- tests/regressiontests/sites_framework/tests.py	(revision 0)
+++ tests/regressiontests/sites_framework/tests.py	(revision 0)
@@ -0,0 +1,34 @@
+from django.conf import settings
+from django.contrib.sites.models import Site
+from django.test import TestCase
+
+from models import SyndicatedArticle, ExclusiveArticle, CustomArticle, InvalidArticle, ConfusedArticle
+
+class SitesFrameworkTestCase(TestCase):
+    def setUp(self):
+        Site.objects.get_or_create(id=settings.SITE_ID, domain="example.com", name="example.com")
+        Site.objects.create(id=settings.SITE_ID+1, domain="example2.com", name="example2.com")
+        
+    def test_site_fk(self):
+        article = ExclusiveArticle.objects.create(title="Breaking News!", site_id=settings.SITE_ID)
+        self.assertEqual(ExclusiveArticle.on_site.all().get(), article)
+    
+    def test_sites_m2m(self):
+        article = SyndicatedArticle.objects.create(title="Fresh News!")
+        article.sites.add(Site.objects.get(id=settings.SITE_ID))
+        article.sites.add(Site.objects.get(id=settings.SITE_ID+1))
+        article2 = SyndicatedArticle.objects.create(title="More News!")
+        article2.sites.add(Site.objects.get(id=settings.SITE_ID+1))
+        self.assertEqual(SyndicatedArticle.on_site.all().get(), article)
+        
+    def test_custom_named_field(self):
+        article = CustomArticle.objects.create(title="Tantalizing News!", places_this_article_should_appear_id=settings.SITE_ID)
+        self.assertEqual(CustomArticle.on_site.all().get(), article)
+    
+    def test_invalid_name(self):
+        article = InvalidArticle.objects.create(title="Bad News!", site_id=settings.SITE_ID)
+        self.assertRaises(ValueError, InvalidArticle.on_site.all)
+        
+    def test_invalid_field_type(self):
+        article = ConfusedArticle.objects.create(title="More Bad News!", site=settings.SITE_ID)
+        self.assertRaises(TypeError, ConfusedArticle.on_site.all)
