Did you know you can drag and drop address from the standard Mail-Address Book to Entourage X? Simply open both address books up and select the addresses you want to move over and drop them in Entourage's Contacts.
There's also a handy Mail folder importer included on the Entourage CD, or it can be downloaded from the MS Mac Office site. Just download the French or German language script and run it... you don't need to know the language as it automatically imports the mail into Entourage.
Mac OS X Hints