http://forum.mamp.info/viewtopic.php?f=1&t=6890

  - Start MAMP PRO.
  - Stop the MAMP Server if it is running.
  - Select File -> Edit Template -> MySQL my.cnf
  - An editor window appears.
  - If a Warning message appears confirm with OK.
  - Find the section "[mysqld]"
  - Beneath the last line of this section add this line:
  - character-set-server=utf8
  - collation-server=utf8_unicode_ci
  - The section "[mysqld]" now looks like this (on my Mac):

<code>
    # The MySQL server
    [mysqld]
    #port      = 9999
    socket      = /Applications/MAMP/tmp/mysql/mysql.sock
    skip-locking
    key_buffer = 16M
    max_allowed_packet = 1M
    table_cache = 64
    sort_buffer_size = 512K
    net_buffer_length = 8K
    read_buffer_size = 256K
    read_rnd_buffer_size = 512K
    myisam_sort_buffer_size = 8M
    bind-address = 127.0.0.1
    default-storage-engine = InnoDB
    character-set-server=utf8
    collation-server=utf8_unicode_ci
</code>

Save (Apple + S) all changes made on "my.cnf"
Close the editor window (Apple + W)
Start the MAMP PRO servers.
You can test the new settings in phpmyadmin, as an sql-query:
show variables like "character%"
show variables like "collation%"