(Sorry my foreign chums, but this is an Australian only thing as far as I know. But to give you an idea of the exchange rate, we are paying $100AU for the standard Halo 3, which equates to about $83US.)
If you're in Australia then you've probably been near an EBgames at one point or another recently, if so you've probably seen that they currently have a deal were you can do a straight trade of ANY three 360 games for Halo 3. You can also do the trade and then pay off the rest for the Collector's Edition.
Normally EBgames trade deals are nothing short of atrocious, but this one is actually kind of sweet. Best of all, you don't actually need to already have games you want to trade to save some dough.
All you need to do is take a trip down to your Cash Converters (I've found them to be great lately for cheap games) and pick up some really crappy launch titles like Kameo for $20. Then you can trade them in. I already had PGR3 and DOA4 from when I bought my 360, but when I went to trade them in the best offer I got was $12 so I just hung onto them. However, through this deal their value is $34. So they've damn near tripled in value!
Anyway, I've rambled on too long. The really interesting bit here is that EB has a deal that isn't the equivelant of being kicked firmly in the nutsack.
So if you were thinking of getting Halo 3, this was a pretty good way to save $40.
(Also a big thanks to Hamza for fixing my name. Your hugs are in the mail)