Cass County Conservancy
- Preserves the history and culture of the county by promoting and financially supporting projects that represent historical east Texas life. Includes projects, resources, and news.
- http://www.cassconservancy.org/

Butterflies of Cass County, Texas
- Information about and pictures of all the known species of butterflies in the county.
- http://www.butterfliesandmoths.org/map?dc=5535&_dcc=1&si=44

Handbook of Texas Online : Cass County
- Current and historical information about Cass County.
- http://www.tsha.utexas.edu/handbook/online/articles/CC/hcc7.html

The Political Graveyard: Cass County
- Lists politicians who lived or died in the county.
- http://www.politicalgraveyard.com/geo/TX/CS.html

Cass County TXGenWeb
- Cass County Texas Genealogy and history data.
- http://www.rootsweb.com/~txcass/

Amphibians and Reptiles in Cass County
- Texas Cooperative Wildlife Collection list of species found in the county.
- http://wfscnet.tamu.edu/tcwc/checklist/CASS034.HTM