I used legal aid, and they were great.
Suggestion: What state of the US are you looking to do your divorce in? Call the Salvation Army in that state and ask them to refer you to free legal aid in that state. They will know what are the best resources in that particular state.
If they don't have a referral for legal aid then ask them to refer you to the women's shelter that they work with, call the women's shelter and ask _them_ for a referral to a legal aid group.
If none of those organizations can help you then look up the "Legal Bar" association for the state, they all have websites, and see if they have a listing for free services. But that is the last option, it is much better to get the _experience_ based referral than to just look it up on a list.
Mike