I'm thinking about traveling to Sydney after Thanksgiving. Not sure what other city (e.g. Melbourne) is worth visiting as well?? I plan on staying in Australia a total of 7 nights.

Depends where your interests lie and your available time, which isn't much. Put it this way, none of Australia's major cities is NOT worth visiting, but it's a long way between them. My suggestion is to rush out and buy a guidebook, a small additional investment, and get some idea of what's on offer. You could then read past threads here (use the Search function) and ask further questions. Sorry, but without knowing what turns you on it's difficult to be any more helpful than this.

I should have said that I don't know exactly when Thanksgiving is, except that it's some time in November, which means that you haven't got much time to make a decision. I'd get that guidebook soon.

The guidebook to get is the AAA Australia because it has things to see in 3 days, then more if you have time. It is a very good overview book and is sold in Barnes and Noble and elsewhere (not just AAA). Neil--Thanksgiving in the US is the fourth Thursday in November. In Canada it is in October (I think). Does Australia have a harvest holiday?
Sally

No we don't, Sally. When I was a kid there was an old English tradition of a Harvest Festival, when the local Anglican church was decorated with farm produce, but there was never a holiday associated with it.

There was a difference between the Pilgrim Fathers and the first settlers in Australia - most of ours arrived involuntarily and were in no mood to give thanks for being here