I just got great news today from Apple.com that now iPhone MMS is available for you that use iPhone 3G and iPhone 3Gs Models and use AT&T phone services. This Multimedia Messaging Service is supported by AT&T, so its not come from Apple.com. So if you use those phones model and AT&T carrier, then you could try this service.
iPhone 3GS MMS is Here (Video)
You could set up this iPhone MMS using the tutorial provided by AT&T from the following link: AT&T: Enabling MMS on iPhone 3G and iPhone 3GS