gistfile1.py

import urlparse
import re

from django import forms
from django.db import models
from django.utils.translation import ugettext_lazy as _


def validate_youtube_url(value):
    '''El patron lo saque de http://stackoverflow.com/questions/2964678/jquery-youtube-url-validation-with-regex'''
    pattern = r'^http(s)?:\/\/(?:www\.)?youtube.com\/watch\?(?=.*v=\w+)(?:\S+)?$'

    if value.startswith(('http://youtu.be/', 'https://youtu.be/')):
        if re.match(r'\w+', value[16:]) is None:
            raise forms.ValidationError(_('Not a valid Youtube URL'))
    elif re.match(pattern, value) is None:
        raise forms.ValidationError(_('Not a valid Youtube URL'))


class YoutubeUrl(unicode):

    @property
    def video_id(self):
        parsed_url = urlparse.urlparse(self)
        if parsed_url.query == '':
            return parsed_url.path
        return urlparse.parse_qs(parsed_url.query)['v'][0]

    @property
    def embed_url(self):
        return 'http://youtube.com/embed/%s/' % self.video_id

    @property
    def thumb(self):
        return "http://img.youtube.com/vi/%s/2.jpg" % self.video_id


class YoutubeUrlField(models.URLField):
    __metaclass__ = models.SubfieldBase

    def __init__(self, *args, **kwargs):
        super(YoutubeUrlField, self).__init__(*args, **kwargs)
        self.validators.append(validate_youtube_url)

    def to_python(self, value):
        url = super(YoutubeUrlField, self).to_python(value)
        return YoutubeUrl(url)

    def get_prep_value(self, value):
        return unicode(value)


try:
    from south.modelsinspector import add_introspection_rules
    add_introspection_rules([],  ["^fields\.YoutubeUrlField"])
except ImportError:
    pass

it is also possible to create validation for vimeo:

https://github.com/kaleidos/django-kvideos/blob/master/kvideos/models.py#L28-L40

And create "django youtube and vimeo field"

I do not have this knowledge for this.
Thanks!!!