List all signals by model and signal type. Tested with Django 1.7.

list_all_model_signals.py

# coding:utf-8

import gc
import inspect
import ctypes
from collections import defaultdict

from django.core.management.base import BaseCommand
from django.db.models.signals import *

try:
    from django.dispatch.dispatcher import WEAKREF_TYPES
except ImportError:
    import weakref
    WEAKREF_TYPES = weakref.ReferenceType,

MSG = '{module}.{name} #{line}'

SIGNAL_NAMES = {
    pre_init: 'pre_init',
    post_init: 'post_init',
    pre_save: 'pre_save',
    post_save: 'post_save',
    pre_delete: 'pre_delete',
    post_delete: 'post_delete',
    m2m_changed: 'm2m_changed',
    pre_migrate: 'pre_migrate',
    post_migrate: 'post_migrate',
    pre_syncdb: 'pre_syncdb',
    post_syncdb: 'post_syncdb',
}


class Command(BaseCommand):
    help = 'List all signals by model and signal type'

    def handle(self, *args, **options):
        signals = [obj for obj in gc.get_objects() if isinstance(obj, ModelSignal)]
        models = defaultdict(lambda: defaultdict(list))
        
        for signal in signals:
            signal_name = SIGNAL_NAMES.get(signal, 'unknown')
            for receiver in signal.receivers:
                lookup, receiver = receiver
                if isinstance(receiver, WEAKREF_TYPES):
                    receiver = receiver()
                if receiver is None:
                    continue
                receiver_id, sender_id = lookup
                
                model = ctypes.cast(sender_id, ctypes.py_object).value
                models[model][signal_name].append(MSG.format(
                    name=receiver.func_name,
                    module=receiver.__module__,
                    line=inspect.getsourcelines(
                    receiver)[1], path=inspect.getsourcefile(receiver))
                )
        
        for key in sorted(models.keys()):
            print '' + key.__module__ + "." + key.__name__, u"({})".format(
                key._meta.verbose_name)
            for signal_name, lines in models[key].iteritems():
                print " "*4, signal_name
                for line in lines:
                    print " "*8, line