When I first began my research of Virginia's court records, I assumed that the Indians which most colonists came into contact with were Tributary Indians. However, I found records of so many Indians living in English colonial households as slaves and servants that I made a separate file of them. These records indicate that it is more likely that that the Indians which most colonists came into contact with on a daily basis were actually slaves.
Here is the file: http://wwww.freeafricanamericans.com/free_Indians.htm

And I just came across this document in Princess Anne County whereby Richard Bell freed his Indian woman servant and her son:
Be it known unto all men...by my own voluntary will for the good services and the good will I bear to my servant maid Eliza. Hill an Indian and her son David have given and granted...deed of gift...full and clear discharge from the service of me and my heirs. 20 March 1748/9 [Deed Book 1747-1755, pages 96-7].
Paul