Google Sync is yet another great offering from Google. From what I understand Google has implemented Microsoft Exchange for users of its Contacts and Calendar apps, such that you can now sync the contacts and calendar on your mobile phone with your Gmail contacts and your Google Calendar events. The syncing is bi-directional, so you can make a change on one or the other, and it will automatically be made on your other devices. This brief article on Wired says that Google Sync "basically solves many of the common problems with contact and calendar syncing in Apple's half-baked Mobile Me service." Note, though, that Google Sync is a beta and there are known problems. This article on the Ars Technica website explains more and notes some of the specific bugs. The Google Sync website has a helpful video explaining what it can do for you.