I've always thought that the lack of iCal todo syncing was one of the strangest omissions on the iPhone and iPod touch. Now, finally, it's possible thanks to Appigo Sync (beta), a free small helper application for the Mac designed to interface with Appigo's $10 Todo iPhone app (iTunes link).
Todo on the iPhone has been able to sync with online services Remember the Milk and Toodledo for a while now. With the addition of Appigo Sync, however, you can now get your todos from iCal (though, unfortunately, it cannot sync with both your Mac and an online service). Like most other desktop syncing solutions for the iPhone, it works over WiFi and requires your iPhone and Mac to be on the same network.
Appigo Sync is a free download. Todo for iPhone is $9.99; there's also a free Todo Lite limited to seven tasks, but which will allow you to test out the syncing (both iTunes links).