How to get there
The 443 bus travels from Circular Quay via Wynyard station and the QVB, and then pops over to Pyrmont, travels all the way up Harris st, drops people off at the casino - directly outside the door of Google. Going back the other way it picks up from underneath the casino at the tram stop, across the road from Google. If you're coming from Town Hall, this is probably your best option. Because it serves the casino, this bus runs every 20 minutes right through until 1am.
If you're coming from Central and don't mind the extra cost ($5.70 return) you can also catch the tram - it both sets down and picks up from the stop under the casino, across the road from Google. Again, serving the casino means that it runs late: every 15 minutes until 11pm, and then every 30 minutes right through till 6am.
Another option if you're coming from Central, or from Ryde (or along Victoria Road between Gladesville and Rozelle) is the 501, which stops a few blocks away; it runs every 30 minutes right through the night.