http://www.spiritualhumanism.org/From their FAQ:
Is this a Christian church?
The Church of Spiritual Humanism is a humanist church, and does not endorse christian theology. Christians are welcome to join but the tenets of the church are not based on the christian belief system. Our central tenant is that Religion must be based on Reason. The church will only endorse beliefs for with evidence verifiable by the scientific method. Since belief in gods is still a matter of faith rather than science we do not yet endorse it. If verifiable evidence of the supernatural is discovered the church be happy to adopt it into our religious system.
And from their Ordination page:
We do require that every one that through ordination accepts "holy orders" from the Church agrees with the tenet that Religion must be base on Reason. By this we mean that the best way of learning about the true nature of ourselves and the universe around has been shown to be the scientific method. If some belief cannot be proven by this method then it will not be endorsed by the Church. As Spiritual Humanist we keep an open mind toward new ideas and will gladly adopt religious beliefs that provide proof.
Ordination means that the Church has authorized the clergy person to perform Marriage, Baby Naming, Funeral, Hand Fasting, Commitment, Affirmation of Love, Invocations, Renewal of Marriage, and holiday ceremonies. Ordained Clergy are prohibited from performing ceremonies that involve exorcism, circumcision and animal sacrifice.
So perhaps contacting the "church" and asking for a list of Ordained Clergy Persons in your area would be a good start?
The major caveat here is that marriage laws vary greatly from state to state (and sometimes even from county to county within states), and your local county offices usually have far more control than they should over who is or is not considered "ordained" or otherwise allowed to perform marriages.
In the case of the big "we ordain everyone!" churches, someone's probably already gone through the hassle of being the first to try to perform a marriage with that ordination in that particular county, so your officiant's job will be easier if they go through the Universal Life Church or one of the other more "established" ones.
Hope that helps. :hi: