I created this Google Group for those who are PHP freaks, not could you post challenging problems to the group, but also you could get challenged by helping in solving any posted problem. This will not only be helpful to those who are new to PHP development but also to those who are veterans, for you get a chance to flex your PHP muscle by dealing with the posted problems  You could visit the group at:
   http://groups.google.com/group/phpdigest

the groups name is PHPDigest