Yeah, sorry, I was just giving credit to the source of the image. The better sites are listed here:
An organization self-described as the Republic of Texas Interim Government asserts, among other things, that the annexation of Texas as a U.S. State was illegal and/or improperly executed, and that the current Texas State government is therefore illegitimate. Their website can be found at http://www.republic-of-texas.net.
Another organization of interest is Texas Constitution 2000, which calls on Texans to ratify a new constitution liberating Texas from the economic and statutory slavery of the U.S. government. Their website is http://www.tcrf.com.
The Independent Nation of Texas website features a FAQ page listing reasons why secession would be good for Texas, as well as links to multiple online resources pertaining to Texas secession, at http://www.anus.com/etc/texas/.