This website probably has been posted here before, but it has a new URL as of a few months ago:
Tennessee Property Data Home Page
It's an extremely useful tool for researching home & land prices in 89 of TN's 95 counties. For example, if you're driving through a subdivision and see some homes you like, just write down the addresses and plug them into the database to see what they sold for (if applicable), their appraised value, and their square footage. You can search & sort by street address, subdivision, sale date and 3 other ways. The "Classification" dropdown menu also gives a bunch of search options.
I recently used this database to help my parents make an offer on a patio home in Church Hill, TN by researching what their future neighbors had paid for their homes.