title: How can I render a ManyToManyField as checkboxes?
body: <p>I'm making a game link site, where users can post links to their 
  favorite web game. 
  When people post games they are supposed to check what category the 
  game falls into. 
  I decided to allow many categories for each game since some games can 
  fall into many categories. 
  So the question is, how do I handle this in my view? 
  And how can I show it as Checkboxes, where at least one has to be 
  checked? 
  And how can I show this as checkboxes in the Admin as well? </p>
  
  <h2>Here is the code</h2>
  
  <h2>Models:</h2>
  
  <pre><code>class Category(models.Model): 
          category = models.CharField(max_length=200) 
          def __unicode__(self): 
                  return self.category 
  class Game(models.Model): 
      name = models.CharField(max_length=200) 
      url = models.CharField(max_length=200) 
      poster = models.ForeignKey(User, related_name='game_poster_set') 
      postdate = models.DateTimeField(default=datetime.now) 
      cats = models.ManyToManyField(Category) 
      hits = models.IntegerField(default=0) 
      post = models.BooleanField(default=False) 
  </code></pre>
  
  <hr>
  
  <h2>Views:</h2>
  
  <pre><code>def submit(request): 
          form = GameForm(request.POST or None) 
          if form.is_valid(): 
                  game = form.save(commit=False) 
                  game.poster = request.user 
                  game.save() 
                  next = reverse('gamesite.games.views.favorites') 
                  return HttpResponseRedirect(next) 
          return render_to_response( 
          'games/submit.html', 
          {'form': form}, 
          context_instance = RequestContext(request),)
  </code></pre>
  
  <hr>
  
  <h2>Forms:</h2>
  
  <pre><code>class GameForm(forms.ModelForm): 
          name = forms.CharField(max_length=15, label='Name') 
          url = forms.URLField(label='URL', initial='http://') 
          class Meta: 
                  model = Game 
                  fields = ('name','url')
  </code></pre>
  
  <p>Thanks! </p>