DAMO (Domino Access for Microsoft Outlook) and the Domino Migration Tool
Move from Exhchange to Lotus but keep your familiar Outlook client.
This is a great article and is a bit technical. It explains at a high-level how to move your company to a Lotus Domino server platform to take advantage of all the features of Lotus Domino but still allow your end users that are more familiar with the Outlook interface to continue using it while reaping the benefits of the more robust Lotus Domino server. Your users can use Outlook, the Lotus Notes Client or Domino web access AT THE SAME TIME, since all your data is stored on the Domino server.