Here's a photo taken in Sydney in late 2009, capturing the lights of Luna Park after sunset. It was shot across the harbour from Blues Point.
I tried a few different exposures, and found about 10 seconds gave good results to capture the lights on the spinning ferris wheel, while still smoothing out the water.

Luna Park at night

Blues Point, Sydney, New South Wales
Canon EOS 50D, 24-70mm f/2.8L @70mm, 10 sec, f/7.1, ISO100