Index: django/conf/global_settings.py
===================================================================
--- django/conf/global_settings.py	(revision 639)
+++ django/conf/global_settings.py	(working copy)
@@ -51,6 +51,11 @@
 # List of locations of the template source files, in search order.
 TEMPLATE_DIRS = ()
 
+# File extensions added to template names when doing something like {% extends "blah" %}.
+TEMPLATE_FILE_EXTENSIONS = (
+    ".html",
+)
+
 # URL prefix for admin media -- CSS, JavaScript and images. Make sure to use a
 # trailing slash.
 # Examples: "http://foo.com/media/", "/media/".
Index: django/core/template_file.py
===================================================================
--- django/core/template_file.py	(revision 639)
+++ django/core/template_file.py	(working copy)
@@ -1,20 +1,21 @@
 "Wrapper for loading templates from files"
-from django.conf.settings import TEMPLATE_DIRS
+from django.conf.settings import TEMPLATE_DIRS, TEMPLATE_FILE_EXTENSIONS
 from template import TemplateDoesNotExist
 import os
 
-TEMPLATE_FILE_EXTENSION = '.html'
-
 def load_template_source(template_name, template_dirs=None):
+    if not TEMPLATE_FILE_EXTENSIONS:
+        raise TemplateDoesNotExist, "Your TEMPLATE_FILE_EXTENSIONS settings is empty. Change it to include at least one template file extension (an empty string is allowed)."
     if not template_dirs:
         template_dirs = TEMPLATE_DIRS
     tried = []
     for template_dir in template_dirs:
-        filepath = os.path.join(template_dir, template_name) + TEMPLATE_FILE_EXTENSION
-        try:
-            return open(filepath).read()
-        except IOError:
-            tried.append(filepath)
+        for template_ext in TEMPLATE_FILE_EXTENSIONS:
+            filepath = os.path.join(template_dir, template_name) + template_ext
+            try:
+                return open(filepath).read()
+            except IOError:
+                tried.append(filepath)
     if template_dirs:
         error_msg = "Tried %s" % tried
     else: