Is there going to be clouds? Always a worthwhile question before one bothers setting up the gear, never fun to then have to take it down as you have been clouded out. So whats one to do but check the weather.
A few of the sites I personally find useful (and there's probably others I dont know about but wish I did)
The Bureau of Meteorology Is a pretty useful choice with its various radars and satellite images.
Brisbane Storm Chasers Good satellite imagery, longer and higher resolution that whats available from BOM for all of Australia.
Skippy Sky More details and map types for things like transparency, seeing, windspeed, clouds etc.
7Timer! Gives a little 3 day forecast of things us astronomers care about
Any other useful sites people can think of for those of us out there who dont know them yet?