This is a Britannica Blog (i.e. sponsored by the Encyclopedia Britannica company) about the recent movie Amazing Grace and about the life of William Wilberfoce which has many infomative links in it, even if many point to a Britannica article. In the first paragraph, there are some links to organizations which are attempting to stop modern slavery which may be useful, including The Amazing Change and Free the Slaves.
One of the links in the article which I wanted to specifically highlight, is an audio link to a BBC program on Wilberforce. I am listening to it just now and it is good.