PBS
Pbs: American Roots Music
If teaching a unit about the history of popular music in America, this PBS web site supporting their four-part TV broadcast of a few years ago would make a great resource. Includes lesson plans and oral histories too.
Other
The Alamo
The online home of historic site of the Mission San Antonio de Valero, commonly known as the Alamo, includes a multimedia introduction, an extensive history of the battle and the mission, and educational resources.
PBS
New Perspectives on the West: Juan Seguin
Juan Seguin, a Mexican American Tejano who helped lead the Texas revolution and independence survived the Alamo but was then exiled from the new state, a victim of prejudice.
Other
Accordions Worldwide: The Tex Mex Sound
This site explains the origins of Tex-Mex music and gives background on its leading contributers.
Texas State Historical Association
Texas State Historical Association: Battle of Medina
A concise synopsis of the Battle of Medina, a part of the Mexican War of Independence against Spanish authority in Mexico.
San Jacinto Museum of History
San Jacinto Museum: Commanders in the Field: Juan Seguin
From this San Jacinto Museum article you can read about Juan Seguin, a man who loved Texas, fought well in the Battle of San Jacinto, but was sent to Mexico because of discrimination.