Two iPad PDF apps - our long-time favorite GoodReader and PDF Expert - have recently incorporated annotation capabilities, turning the iPad into a PDF reviewing and commenting device.
The details of how iTunes and MobileMe syncing work keep changing through successive versions of the iPhone OS. "Take Control of Syncing Data in Leopard" author Michael E. Cohen explains how each version has worked, and how to prevent duplicate calendar events from appearing on your iPhone or iPod touch.
Autofill, the iTunes feature previously available only for the iPod shuffle, is now available for all iPods that are set to manage music manually. Unfortunately, finding and using the Autofill feature can be a challenge. Michael Cohen takes you through the steps to track it down.
I'm a fan of Mark/Space's syncing products. The Missing Sync for Palm OS, for example, has made my wife's digital life much more pleasant now that she no longer has to deal with the not-always-reliable collaboration between Apple's iSync and Palm's HotSync conduit to get her Palm TX and her PowerBook G4 on the same page