There are several media-pushing services represented at the opening of the iTunes App Store, each with their own combination of supported sites. ShoZu (covered here) remains the whopper of them all with support for roughly 30 popular social sites and services. There are the major players, of course--Facebook, Twitter, Flickr, Photobucket, Blogger, Picasa, LiveJournal--but ShoZu isn't too high and mighty to upload text and images to some of the more niche guys, like Box.Net qipit, Snapfish, and SmugMug.
With so many services ready to cram into an app interface, things could get tangled up fast. But they don't, partly due to the iPhone's nice big screen and partly due to a structure designed to keep order. Frequent uploaders can automate multi-platform-pushing by going online and adding up to 10 child services to be copied each time media is posted to the parent service.
My biggest gripe? That while you can sign up for a ShoZu account from the iPhone itself, you have to visit the Web site to arrange for multi-pinging. It's the glue that ties ShoZu together for many users, and is something they'll need to add to truly be a standalone app on the iPhone.