Try www.4team.biz. They have a tool that will allow you to create a file with all of your contacts as vCards, which can be imported into Entourage. I tried the trial - it works, but is limited to 5 contacts at a time. You'll have to buy it to do more than that. Looks like it should work for one time migration of your contacts. Ongoing synchronization between the two platforms is a different problem.