Another vote for blue mountains here. Also Taranga zoo in Sydney, try go later in the day as the views over the whole of sydney are amazing
+1. Did a good minibus tour of the blue mountains.
Went so long ago any recommendation on restaurants would be well out of date
Sydney - Did go and take a tour around the Olympic stadium. Its not that exciting I suppose, but did kick yself when we got to the pool, didn't take swimming trunks - a swim in the pool was included.
Melbourne - hired a car and drove down the Great Ocean Road a bit, came back on some ferry and stopped off for fish and chips. Did Philip Island for the blasted ice rats- stayed and there was a spider in the shower. Didn't go near it. Got laughed at as it was a "common brown" apparently.
Now had you been going to Brisbane I had a couple of other better suggestions. But you aren't. Boo.