There are many useful resources available to trace your ancestry.  

1. African Ancestry Article:
CNN and Fortune published a great article last year you may find interesting.  See below: 

African Ancestry uses DNA to trace black American's lineages - February 19, 2007  

2.  Tracing Your Roots:
You may also want to visit www.ancestry.com to begin tracing information about your branch on the family tree.  It's important that you know the maiden names of the women on your branch because the system cannot provide good information using married names.  Also, please note there is a fee for using this service but it's worth it when you find new information about your family.

3. What's in a name?
Most people know slaves were given the names of the families that owned them.  But understanding the origin and meaning of names is imporant.  I found this link on the origin and history of the Armstead family name and thought you might like to see it.  Did you know name Armstead has a meaning?  It's "ever ready or always prepared."  You will also see the official crest established for those bearing the Armstead name.  You may want to read about the origin of your individual family name also.  Items bearing family names and crest can be ordered.

http://www.houseofnames.com/fc.asp?sId=&s=Armstead