I am new to apple and arduino both. I recently switched from a windows machine to a mac and I also bought the pre-programmed atmega328 chip. Is there a way to make this work with arduino for os x?
Thanks,
Ryan
If it's pre-programmed, you just need the right description of the chip in your Arduino IDE's "boards.txt" file. That file should be found in your Arduino installation directory.
There are a couple of different "pre-programmed 328" vendors, and they may have different versions of the bootloader. Everything should work fine for either version, but the settings in boards.txt may depend on which vendor sold your chip. As of this writing, the 328 stuff is all very "bleeding edge" and subject to changes as such variations become standardized.
Usually, switching platforms should be done one step at a time, to ensure you know the implications of each switch. Getting a new OS, new board system, and a new chip for the board system, all at once, well that's either daring or... well, daring. 
On that note, when can we expect some standardised Atmega 328 goodness on our arduino boards?
I'm quite sure that a version 13 of the Arduino environment with support for the 328 is in the works and will be out before long .-)
I think Gav meant, when can we expect a 328 sold on a Duemilanove or a successor board. Since 'Duemilanove' means '2009', and it's now February of 2009, I would imagine the next reference design might be a while. Vendors might go through the trouble of swapping out chips, but that seems like an extra cost that they'd have to pass on to the customer. A lot can be done on a 168... challenge yourself and be patient, or do some extra work yourself if you really need the 328.
I mailed back an forth with the guy selling the Iduini board. He is willing to sell Iduinos with the 328 now.