Index: no/no_municipalities.py
===================================================================
--- no/no_municipalities.py	(revision 0)
+++ no/no_municipalities.py	(revision 0)
@@ -0,0 +1,32 @@
+# -*- coding: iso-8859-1 -*-
+"""
+An alphabetical list of Norwegian municipalities (fylker) fro use as `choices`
+in a formfield.
+
+This exists in this standalone file so that it's on ly imported into memory
+when explicitly needed.
+"""
+
+MUNICIPALITY_CHOICES = (
+    ('akershus', u'Akershus'),
+    ('austagder', u'Aust-Agder'),
+    ('buskerud', u'Buskerud'),
+    ('finnmark', u'Finnmark'),
+    ('hedmark', u'Hedmark'),
+    ('hordaland', u'Hordaland'),
+    ('janmayen', u'Jan Mayen'),
+    ('moreogromsdal', u'Møre og Romsdal'),
+    ('nordtrondelag', u'Nord-Trøndelag'),
+    ('nordland', u'Nordland'),
+    ('oppland', u'Oppland'),
+    ('oslo', u'Oslo'),
+    ('rogaland', u'Rogaland'),
+    ('sognogfjordane', u'Sogn og Fjordane'),
+    ('svalbard', u'Svalbard'),
+    ('sortrondelag', u'Sør-Trøndelag'),
+    ('telemark', u'Telemark'),
+    ('troms', u'Troms'),
+    ('vestagder', u'Vest-Agder'),
+    ('vestfold', u'Vestfold'),
+    ('ostfold', u'Østfold')
+)
Index: no/__init__.py
===================================================================
Index: no/forms.py
===================================================================
--- no/forms.py	(revision 0)
+++ no/forms.py	(revision 0)
@@ -0,0 +1,75 @@
+# -*- coding: iso-8859-1 -*-
+"""
+NO-specific Form helpers
+"""
+
+import re, datetime
+from django.newforms import ValidationError
+from django.newforms.fields import Field, RegexField, Select, EMPTY_VALUES
+from django.utils.translation import gettext
+
+class NOZipCodeField(RegexField):
+    def __init__(self, *args, **kwargs):
+        super(NOZipCodeField, self).__init__(r'^\d{4}$',
+            max_length=None, min_length=None,
+            error_message=gettext(u'Enter a zip code in the format XXXX.'),
+            *args, **kwargs)
+
+class NOMunicipalitySelect(Select):
+    """
+    A Select widget that uses a list of Norwegian municipalities (fylker)
+    as its choices.
+    """
+    def __init__(self, attrs=None):
+        from no_municipalities import MUNICIPALITY_CHOICES # relative import
+        super(NOMunicipalitySelect, self).__init__(attrs, choices=MUNICIPALITY_CHOICES)
+
+class NOSocialSecurityNumber(Field):
+    """
+    Algorithm is documented at http://no.wikipedia.org/wiki/Personnummer
+    """
+    def clean(self, value):
+        super(NOSocialSecurityNumber, self).clean(value)
+        if value in EMPTY_VALUES:
+            return u''
+
+        msg = gettext(u'Enter a valid Norwegian social security number.')
+        if not re.match(r'^\d{11}$', value):
+            raise ValidationError(msg)
+
+        day = int(value[:2])
+        month = int(value[2:4])
+        year2 = int(value[4:6])
+
+        inum = int(value[6:9])
+        self.birthday = None
+        try:
+            if 000 <= inum < 500:
+                self.birthday = datetime.date(1900+year2, month, day)
+            if 500 <= inum < 750:
+                self.birthday = datetime.date(1800+year2, month, day)
+            if 500 <= inum < 1000:
+                self.birthday = datetime.date(2000+year2, month, day)
+        except ValueError:
+            raise ValidationError(msg)
+
+        sexnum = int(value[8])
+        if sexnum % 2 == 0:
+            self.gender = 'F'
+        else:
+            self.gender = 'M'
+        
+        digits = map(int, list(value))
+        weight_1 = [3, 7, 6, 1, 8, 9, 4, 5, 2, 1, 0]
+        weight_2 = [5, 4, 3, 2, 7, 6, 5, 4, 3, 2, 1]
+
+        def multiply_reduce(aval, bval):
+            return sum((a * b) for (a, b) in zip(aval, bval))
+
+        if multiply_reduce(digits, weight_1) % 11 != 0:
+            raise ValidationError(msg)
+        if multiply_reduce(digits, weight_2) % 11 != 0:
+            raise ValidationError(msg)
+
+        return value
+