Something

class PresentationForm(forms.ModelForm):
    cat = forms.ModelChoiceField(Category.objects.all(),label=u'Category')
    audiences = forms.ModelMultipleChoiceField(AudienceType.objects.all())
    title = forms.CharField()
    short_abstract = forms.CharField(widget=forms.Textarea,min_length=1,max_length=5000,help_text="A short abstract less than 500 words")
    status = forms.CharField(widget=forms.HiddenInput,label=u'',initial='Pending')

    class Meta:
        model = Presentation
        fields = ('cat', 'audiences', 'title', 'short_abstract')
        exclude = ['status']