I needed to display a block of user profiles, order by their birthday (upcoming birthdays).
The block displays the upcoming birthdays for the first 5 users. For the moment everything is hard-coded, but feel free to sumbit a patch to change it to settings.
Variables you probably need to change:
$table = 'field_data_field_user_geboortedatum';
$field = 'field_user_geboortedatum_value';
$view_mode = 'verjaardag';
$limit = 5;