UPDATE: Its mostly crap. Read my edit at bottom of thread.
Juice Wireless, Inc, has just released Flutter (iTunes AppStore Link), an AppStore app which (kinda) allows you to send MMS from your iPhone.
The app is definitely still in a beta format, with a bunch of supposed limitations (can only send to folks in your contact book - can't just tap in a number, can't receive MMS, location support is buggy - far off usually, and not everyone seems to be receiving the MMS's), but its up.
However, either the app is a joke, or their servers are much more overloaded than they thought would happen - I have yet to even get the confirmation sms, much less be able to test the app, and its been hours. I will update this post with a more involved review when (if?) it comes through.
How bout you guys? Anyone able to get this working?
Notable - as of this writing, the app isn't in the AppStore on the iPhone, only via the link I posted.
EDIT: Alright, I was finally able to get my SMS password sent to me after pressing resend a dozen times (after which I got it a half dozen times, ha). I sent an "MMS" to my T-Mobile phone, and received it less than a minute later.
All it was, though, was a message saying "You've received an iPhone picture message" and a "click here to view it." The link directs to a mobile page in the receiving phone's browser (assuming, of course, they even have a browser, and internet on their phone), which loads the image. Lame. Even that didn't work though - it told me I was an unauthorized viewer and that "this JuiceCast is unavailable."
Save your time, don't download this.