Palringo is a free multi-client instant messaging app for mobiles that hit the App Store over the weekend, and it's the first to officially support Google Talk/Jabber, on top of Windows Live Messenger, Yahoo, ICQ, iChat and Gadu-Gadu (if you're in Poland). You can also use it to quickly send photos from your camera or photo albums to anyone on any of your buddy lists, who will see an inline image (if supported) and a link to a bigger (but still compressed photo) on Palringo's servers. Not MMS, but the feature works as advertised. It's great I can use GTalk on the iPhone now, but again, this is something we've been able to do via jailbreak and Installer.app for a while.