An excerpt from a recent article on that very subject:
"Government textbooks and the Texas Constitution say that ours is a weak-governor state. A strict constructionist would insist that the governor’s power is largely limited to making appointments to state boards and commissions and to vetoing bills.
In practice, the political power of the governor has expanded dramatically over the past four decades. Governor Perry has upended the political culture by establishing what amounts to a cabinet form of government.
The governor’s office isn’t just a power center; it is the power center. Every high-level appointee answers to Perry. Every agency head answers to Perry. He is able to dominate the Legislature in ways no governor before him did. Perry’s will to power has reshaped the traditional leadership roles. Before he came along, it was acknowledged that the lieutenant governor was the state’s most powerful official.
This situation is not entirely of Perry’s making. The cultural change that paved the way for the governor’s office to become
the power center of state government was the arrival of two prominent politicians. These were, of course, Ann Richards and George W. Bush, our first modern celebrity governors."
snip...
In addition to appointing commissioners and governing boards of state agencies, including the boards of regents of public university systems, the governor appoints members of task forces and other advisory groups, such as the Task Force on Appraisal Reform and the Texas Tax Reform Commission. The Governor also appoints individuals to fill the remainder of certain elected offices, including the judiciary, following the death or resignation of the office holder. It is estimated that a governor will make 3,000 appointments over the course of a four-year term.
http://www.senate.state.tx.us/75r/senate/members/dist16/pr07/p073107a.htm
snip
A significant resource that governors may use to build support and accomplish political goals is the power of appointment. About 200 boards, commissions, and agencies oversee the daily operation of government, and the governor makes several hundred appointments to these various entities.
Texas Politics - The Executive Branch