Doing a conditional aggregate (e.g. count(*) if x=y) in postgres?

All;
Is there a way to get a conditional aggregate? I have this two column view:

SELECT count(*) AS count, xx_plan.plan_name
FROM xx_membership
JOIN xx_account USING (account_id)
JOIN xx_plan USING (plan_id)
WHERE xx_membership.status = 10
GROUP BY xx_plan.plan_name;

And would like to add additional columns (not rows) breaking out
"status=20" and "status=30" totals.
Is this possible without a stored procedure?