According to the Genealogy in Time newsletter,

the Tennessee State Public Library has put online a collection of some 1,500 family bibles that the library has been collecting since the 1920s. The collection consists of scans of all the pages in the bibles that contain notations such as dates of birth, baptism and marriage of various family members. In Tennessee, birth certificates were not required until 1908, making this collection particularly valuable for anyone with Tennessee ancestors (interesting fact: the US government still accepts a list of births in a family bible as one proof of citizenship).

When using Bible records, a number of things you should take into consideration include:

• The information has NOT been checked to ascertain whether it is valid or not.
• Families MAY have altered the date of a marriage in the Bible to make it look like the children were NOT conceived out of wedlock.
• If the cause of death is included in the Bible, it may be different than the official record.
• Some wealthy families may have also recorded the names and dates of birth of their slaves.

This collection can be searched by name. Access is free. [Tennessee Bible Records]