Simple M2M filter for Django admin.

gistfile1.py

class M2MFilter(admin.SimpleListFilter):
    title = _('yourm2mfield')

    # Parameter for the filter that will be used in the URL query.
    parameter_name = 'yourm2mfield'

    def lookups(self, request, model_admin):
        return ((x.pk, x.title) for x in YourRelatedModel.objects.all())

    def value(self):
        """ Splits a comma-separated string of PKs into a list of
            integers. """
        try:
            values = [
                int(pk) for pk in self.used_parameters.get(
                    self.parameter_name, '').split(',')]
        except ValueError as e:
            return []
        else:
            return values

    def queryset(self, request, queryset):
        """ Returns the filtered queryset based on the value provided
            in the query string and retrievable via `self.value()`. """

        value = self.value()
        return queryset if value is None \
            else queryset.filter(yourm2mfield__pk__in=value)