I've been using these guys for years; highly recommended.
I usually get NRMA sending me greenslip renewal notices and they're always much higher than what I last paid so I always check on the above site.
Surprisingly NRMA's value on the site is around half of their renewal notice. NRMA try to rip off existing customers with high rates; instead of renewing via the NRMA form they send, you can just go online and do a new renewal from NRMA (or whoever is cheapest) at a lower rate.
Crazy!
s