<form action='/busket/' method='post'>
    <input type='hidden' name='order' value='{{ the_model }} {{ gadget.brand_name }}'>
    <input type='submit' value='добавить в корзину'>
</form>

def busket(request): 
    if request.method == 'POST' and 'order' in request.POST:
        if 'bucket_list' not in request.session:#Bucket_list variable it's a joke - just like this pic)
            request.session['bucket_list']=[]
        order = request.POST['order']
        bucket_list = request.session['bucket_list']
        bucket_list.append(order)
    elif 'bucket_list' in request.session:
        bucket_list = request.session['bucket_list']
    else:
        empty_order = True
        return render_to_response('busket.html', {'empty_order': empty_order,}) 
    return render_to_response('busket.html', {'bucket_list': bucket_list,})

{% if empty_order %}
    <h3>Ваша корзина пуста</h3>
{% else %}
    {% for x in bucket_list %}
        {{ x }}
    {% endfor %}
    <a href='/order/'>Купить</a><br>
    <a href='/catalog/'>Выбрать еще чё-нибудь</a>
{% endif %}

#Django is optimising the sessions. By default, session saving only if it was modified.
#List are reference object, and it's determined by reference, so for Django it's remains the same object.
#Tuple are atomic object, so it's determined directly and session is modified every time when modified the tuple.
def busket(request):
    if not isinstance(request.session.get('bucket_list', None), tuple):
        request.session['bucket_list'] = ()
    if request.method == 'POST' and 'the_model' in request.POST:
        order = request.POST['the_model']
        request.session['bucket_list'] += (order, )
    if not request.session['bucket_list']:
        empty_order = True
        return render_to_response('busket.html', {'empty_order': empty_order,}) 
    bucket_list = request.session['bucket_list']
    return render_to_response('busket.html', {'bucket_list': bucket_list,})