Check out these websites where you can also post your resumes:

http://www.cnmdallas.org/opportunity_501.aspx - Opportunity 501 is a cost-effective method for nonprofit organizations to recruit qualified personnel and to assist individuals seeking nonprofit jobs in Texas:

http://www.txnp.org/jobs/jobsearch.asp - The most significant nonprofit portal in Texas, TexasNonProfits.org provides data that facilitates connections between the 80,000+ nonprofit organizations with the 4,000+ charitable foundations in the state of Texas, major philanthropic corporations and sharing individuals.  

www.idealist.org
www.us.oneworld.net
www.NonprofitOyster.com
www.casefoundation.org
www.OpportunityKnocks.org
www.nonprofit-jobs.org/
www.nonprofitcareer.com/
www.jobsinnonprofit.com/
www.deepsweep.com/
www.Charity.org
www.ajcjobs.com (they have a non profit section)