While requests to use Microsoft Dynamics CRM and CRM Online from a Mac are not terribly frequent, it comes up every once in a while so it is definitely worth addressing.

Supported clients for Dynamics CRM include Internet Explorer 6 (SP2) and later, and Outlook 2003 (SP2) and later.  Unfortunately, Entourage is not a supported client.  And, supported operating systems are all of the Windows flavor.

So, while there's no direct method to do this, there's always a way, right?  Here's a compilation of ideas.

1. Use Virtual PC, Parallels or Bootcamp software to run Windows on the Mac
2. Utilize a Citrix/Terminal Server connection.
3. Read Sonoma Partners' blog on using Firefox with the View Page in IE Tab add-in.: http://blog.sonomapartners.com/2007/11/microsoft-crm-r.html
4. Read John Straumann’s thoughts on a J2EE approach: http://mscrmguy.blogspot.com/search/label/MSCRM%20on%20a%20MAC%3F
5. Read Ben Vollmer’s blog entry from a while back: http://blogs.msdn.com/midatlanticcrm/archive/2006/08/15/Using-Microsoft-CRM-with-a-Mac.aspx

Keep in mind that none of these methods are supported, but that's not to say they won't work.

HTH - Kevin