There are several organizations in the state that provide free legal assistance and information directed at non-profits:
Texas Association of Nonprofit Organizations
This site has information on legislative advocacy, provides legal advice, information on educational opportunities and grant writing, job openings, and much more.
Center for Community-Based & Nonprofit Organizations
This site has a list serve you can subscribe to which will inform you of events of interest, educational opportunities etc. There is information on many workshops and conferences, a great section of helpful resources, and much more
Texas C-Bar
Texas Community Building with Attorney Resources ("Texas C-BAR") is the only project of its kind in Texas, providing free business law services across the state to community-based nonprofits developing affordable housing and other much-needed services in low-income communities. To be eligible the primary mission of the organization is to help low-income persons. This site also provides information on becoming a non-profit organization and legal/tax issues and information on workshops being held across the state which address those issues.