The best antique show in Texas is the Roundtop Antique Weekend. "Weekend" is a misnomer. It really lasts for almost 2 weeks. It is located half way between Austin and Houston. The next show is March 24-April 4.
http://www.antiqueweekend.com/indexmain.html
This is by far the largest and best show in Texas for antiques and collectibles. Canton used to be a good antique market but it is more a new and craft show now. The Roundtop show is held twice a year and I have been to the last 6 shows. If you have any questions let me know.
Jay