Drawing a blank on some SQL

Hi,

I'm just drawing a blank entirely today and would appreciate some help on
this.

The long and short; there are 12 distinct activities that need to be queried
on a weekly basis:

SELECT count(activity_id), activity_id
FROM foo_activity
WHERE created >= '01/01/2011' and created < '01/08/2011'
GROUP BY 2
ORDER BY 2;

It gives me this answer, which is correct:

count | activity_id
-------+---------------------
1502 | 1
11 | 2
2 | 3
815 | 4
4331 | 7
30 | 9
1950 | 10
7 | 11
67 | 12

But what I need to see is if there are no activities for the particular
activity_id that week, that it lists the count as 0 and lists the
activity_id associated like this:

count | activity_id
-------+---------------------
1502 | 1
11 | 2
2 | 3
815 | 4
0 | 5
0 | 6
4331 | 7
0 | 8
30 | 9
1950 | 10
7 | 11
67 | 12

Thanking you in advance for any help on this. The caffiene seems to be not
working well today.

Aaron