The Texas Tomorrow Fund Texas Guaranteed Tuition Plan is currently closed to all new enrollment.
However, there is the "Tomorrow’s College Investment Plan", which provides a tax-advantaged investment vehicle for college savings. The plan includes a choice of 20 different investment portfolios and offers the opportunity for tax-free growth of your investments and tax-free withdrawals on earnings used for qualified education expenses.
http://www.texastomorrowfunds.org/ttf_overview.html