DataCase at the iTunes App Store allows you to turn your iPhone or iPod into a wireless storage devices that can be accessed by other network devices.

Features:
DataCase keeps your files close by turning your iPhone or iPod Touch into a hand held wireless drive.
Drag and drop files just like it was another hard drive.
DataCase makes it easy to view your Documents, Audio, Video, and Photos on you iPhone.
Works with any computer that has wireless capabilities or is connected to a wireless network.
DataCase allows you to create multiple volumes to separate your data any way you like.

Cheep, and probably worth a test drive