Both Lotus Notes and Outlook have the options to "Export" the address book to a tab or comma delimited file (CSV format). When you do this save the file to the PC desktop then burn the file to a cd or copy it to a flash drive so that you will be able to transfer them to your Mac. Then open the program on the Mac that you want to use for your addresses (that could be Outlook, or Excel, etc,) and import the delimited file using the Import or Open command.
Hope this helps. Let me know if you have any questions.