Centos 5.4 - while it looks like a good choice, there has been some political infighting going on recently which makes us a little nervous about its future. In addition we have found that a number of the core packages we wish to use are out of date (postfix, dovecot, amavisd-new among them).
Centos 5.x is my selection. You can also use packages from epel and dag's rpm repositories.
-- Eero
