...other cell phone services than Cingular?

No. They have an exclusive agreement until 2009.

It'll only be with Cingular. But I'm sure as with any GSM phone, you'll be able to find an unlocked iPhone at a premium (additional $100-300) and use it another GSM network (i.e. T-Mobile)If you're not sure what I mean by unlocked, it's basically this. All phones sold by these Service Providers like T-Mobile, Cingular, and Verizon are "locked" so that the phone only works with their network only. But unlock codes exist for every single phone (you can just call your provider and they can give it to you) so that you can use that phone on other networks. For instance, if you really like the phone you're using with Cingular, but you hate the Cingular service, you can switch to T-Mobile service and call Cingular to get the unlock code for your phone so that you can use the same phone with your new T-Mobile service.Anyways, a lot of those mom n pop wireless stores sell phones that are already unlocked to work with all networks. So if you really wanted the iPhone and you don't want to switch from T-Mobile, just look for an unlocked iPhone. Just be ready to pay up to $800-900 for it. Ridiculous, I know, but that's how this market operates right now.

Rogers Wireless of Canada is set to get the iPhone as well.