I know nothing about iPods and iPhones and iToasters and such, so I asked my husband who considers himself an expert on the subject. He says you have to get it from the Apple Store. You cannot install anything on your phone (unless it's hacked somehow) that does not come from Apple.

That being said, you can create an iPhone-optimized web application that'll run on a website that iPhone users can navigate to. It's not quite the same, but it's an option.

My husband also says that Apple maintains full and utter control over anything in their store -- they are judge, jury, and executioner of such matters and are not porn friendly. (I thought I heard somewhere that the first adult app had finally been approved).

Developers are charged $99 (or somesuch) to put their software in a store. He isn't sure if that's an annual fee, or if it's to register as a developer, or what. But basically it costs a few bucks to put stuff in the iPhone app store to avoid being inundated with crappy programs.

--Aaron