Little Machines Office2Mac is a great program.
It's only $10. Yes, that might seem expensive for a 1-time transfer, but it makes it so much easier (compared to other options I was able to find), for transferring everything from Outlook- email, contacts, datebook (I didn't need to transfer appointments but I think it does those too.)
You might be able to find some hacked together process involving migrating first to Thunderbird, then burning a DVD in Linux, then spreading pixie dust on it before importing into your Mac. But O2M really is as easy as their web site says.
The best thing was that I was able to maintain categories for contacts and folders for stored emails, by selectively importing batches of data.