iTunes 7.7
Use iTunes 7.7 to sync music, video, and more with iPhone 3G, and download applications from the iTunes Store exclusively designed for iPhone and iPod touch with software version 2.0 or later. Also use the new Remote application for iPhone or iPod touch to control iTunes playback from anywhere in your home — a free download from the App Store.

iTunes 7.7 is available via Software Update and is also available as a download at Apple's website.

App Store
Downloadable apps are now available at the iTunes App Store.  Several free applications such as AOL's AIM Application and Apple's free Remote Application which allows you to "control the music on your computer or Apple TV from your iPod touch or iPhone. Play, pause, skip, shuffle. See your songs, playlists, and album art on your iPod touch or iPhone as if you were right in front of your computer. Remote works with your Wi-Fi network, so you can control playback from anywhere in and around your home."

Over 500 applications are available today and iTunes 7.7 is required.