I saw this non-profit mentioned in this month's Oprah Magazine. Loved Twice is a non-profit that accepts gently used baby clothes for mothers who can't afford them. They are distributed through social workers in hospitals, shelters, and clinics to helped disadvantaged children.
There are a lot of drop off centers in California but you can also mail clothes to the organization. I have a ton of bibs that my daughter has recently stop using so I'm sure this organization would put them in good use because they are still in great condition.
There are locations throughout the US that you can mail the clothing to which might be closer to you than California. Please go to http://lovedtwice.org/how-to-help/give-clothes/ to find the nearest location to you.