Very possibly, yes. Entourage, Address Book and iCal are all compatible with Apple's built-in iSync technology. All that remains is to figure out if your phone, PDA or other external device is also recognized by iSync. Luckily, Apple keeps a list of compatible devices!

They also have a comprehensive list of help articles for connecting particular devices to your Mac. With iSync and your mobile device, your data can go everywhere you go.