I have a TIM sim card from Italy and I'm the US and need to buy a BlackBerry 8900 Curve, the only one available is through ATT. Will my Italian sim card work?

It will work once you get the 8900 unlocked.
I'd recommend http://www.gsmphonesource.com for an unlock code. Very fast, and I've used them dozens of times without a problem.

Tmobile also has the 8900. They look a little different.

There is a new device coming out that will be for sale that will be completely unlocked. You wont need a SIM to get data, just use the wifi. I hear it will be for sale on CDW. Anyone else heard of it? I believe it is an 8900.

Wow.
Any information (proof) about this one?

It is something I heard about that is supposedly in testing. Just wondered if anyone else had seen or heard something. If they do offer it, it will be really cool. That would mean you wouldnt have to pay for data coverage.

This certainly sounds more definitive than your other posts.

RIM had this device once - the 7270. WiFi (and SIP) only. Carriers weren't thrilled.

So it's possibly, maybe, a rumor.