Exporting Address Books from Eudora 6.0.1 to Apple Mail
There is a really neat free program that directly converts Eudora address books to Apple Mail address books. The program is called Eudora Mailbox Cleaner and is in the Archive: archive>macintosh>inbox>eudora mailbox cleaner>
How it works: Drag the Eudora Folder of the user (where all the address groups are) onto the Eudora Mailbox Cleaner icon in the Finder and it will convert the address book.
The program might also copy over the Eurdora mailboxes to Mail, so delete those if they get copied.
If you can't get to the archive, the link to the page with the program is: