ISync is will let you mount your iPhone (or iPod Touch) on a Mac as a WiFi external drive. Right now it's only good for data storage: a folder on the Mac is synched with a folder on the iPhone, but developer Francisois is working on wireless iTunes synching (which will involve tricking iTunes into seeing the iPhone as a USB mounted iPod).
ISync uses the open source rsync to do the heavy lifting, but it has a nice, staight forward GUI for both installation and use. Of course, you'll need a jailbroked iPhone to do this, and I'll be trying this out on an iPod Touch later today. Stay tuned.
Project page [Google Code via Everything iCafe]
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