As mentioned, there is a new viewing area on Dunreath Avenue, which is the ring road between the domestic and international terminals. Drive along Dunreath and watch for the brown coloured signs. It affords great views of heavies taking off from RWY03 where, if you're lucky, they'll taxi right past the viewing area before turning off Mike onto the end of RWY03. Alternatively, you get to see planes rotate from RWY21.
The down side, however, is that it's not open 24 hours. During the winter months, it closes at 1730. Night shots, therefore, would be quite difficult, which is a shame.
There is also a viewing deck at the International Terminal, but parking there is expensive, and you're stuck behind a glass window, which may be quite dirty. The other option is to go airside at the Domestic Terminal - which is still permitted even if you're not travelling. You just have to pass security like everybody else. Parking, again, is expensive.
Boeing 777 fanboy