A handful of snippets

from django.utils.cache import cache
from django.http import HttpResponseForbidden

def throttle_post(func, limit=3, duration=900):
    def inner(request, *args, **kwargs):
        if request.method == 'POST':
            remote_addr = request.META.get('HTTP_X_FORWARDED_FOR') or \
                          request.META.get('REMOTE_ADDR')
            if cache.get(remote_addr) == limit:
                return HttpResponseForbidden('Try slowing down a little.')
            elif not cache.get(remote_addr):
                cache.set(remote_addr, 1, duration)
            else:
                cache.incr(remote_addr)
        return func(request, *args, **kwargs)
    return inner

from django.db.models.loading import get_model
from django.db.models.query import QuerySet
from django.db.models.fields import DateTimeField, DateField

register = template.Library()

@register.filter
def latest(model_or_obj, num=5):
    # load up the model if we were given a string
    if isinstance(model_or_obj, basestring):
        model_or_obj = get_model(*model_or_obj.split('.'))

    # figure out the manager to query
    if isinstance(model_or_obj, QuerySet):
        manager = model_or_obj
        model_or_obj = model_or_obj.model
    else:
        manager = model_or_obj._default_manager

    # get a field to order by, defaulting to the primary key
    field_name = model_or_obj._meta.pk.name
    for field in model_or_obj._meta.fields:
        if isinstance(field, (DateTimeField, DateField)):
            field_name = field.name
            break
    return manager.all().order_by('-%s' % field_name)[:num]

from django.conf import settings
from django.db.models.query import QuerySet
from django.utils.cache import cache
from django.utils.hashcompat import md5_constructor

def stringify_object(obj):
    if isinstance(obj, QuerySet):
        return obj.query.as_sql()
    return unicode(obj)

def key_from_args(*args, **kwargs):
    strings = []
    for arg in args:
        strings.append(stringify_object(arg))
    for k,v in kwargs.items():
        strings.append('%s=%s' % (k, stringify_object(v)))
    return md5_constructor(''.join(strings).hexdigest())

def cached_filter(func, timeout=300):
    def inner(*args, **kwargs):
        if settings.DEBUG:
            return func(*args, **kwargs)
        cache_key = key_from_args(*args, **kwargs)
        result = cache.get(cache_key)
        if not result:
            result = func(*args, **kwargs)
            cache.set(cache_key, result, timeout)
        return result
    inner._decorated_function = func
    return inner