Many of these sights are covered in The Book, but with some additional information here.
The Texas State Historical Association has created an online Handbook of Texas with entries on almost every topic of Texas history. They have also created a separate online Handbook of Houston History, a good resource for a wide range of Houston history topics. I have contributed 23 articles to the Houston handbook.
2.1 The Texas Revolution in Houston - book excerpt
2.2 Charlotte Allen, the true story
2.3 Texas' Long Lived Legacies from Richard Coke
2.4 The Civil War and its Aftermath in Houston - book excerpt
2.5 Slavery, the Confederacy and Jim Crow on the streets of Houston - partially excerpted from the book
2.6 How many flags over Texas?
4. Houston's Cemeteries - site maps and brief bio's for notable burials
4.1 Beth Israel Cemetery
4.2 College Park Memorial Cemetery
4.3 Forest Park Lawndale Cemetery
4.4 Glendale Cemetery
4.5 Glenwood and Washington Cemeteries
4.6 Hollywood Cemetery
4.7 Holy Cross Cemetery
5. Early industrial sites on Buffalo Bayou
7. Houston professional baseball history
8. History of the Houston Medical Center
10. Houston's gay community; the Paul Broussard murder legacy