This is an importatnt online resource for finding documents, letters, papers that are held in various collections in VA.
For example - I used the search engine and typed in one keyword "slaves" and got over 400 hits.
You then click and go to the hit - where you can get a description of what is contained in the collection - here's one description I found:
"Permission and character certificates, 1832-1860, for slaves seeking to join Bethel Baptist Church in Clarke County, Virginia. Bethel Baptist Church was in Frederick County, Virginia until 1836 when Clarke County was formed. "
A very useful site.
Denise