Houston's a city of great giving and the CultureMap Charity Challenge, presented by Yellow Cab, aims to highlight that. CultureMap selected 12 deserving nonprofits to compete for a grand prize as they all raise awareness for worthy causes. CultureMap is highlighting the charities over the next several weeks. Today: Ambassadors for Texas Children's Hospital.

Since 2009, Ambassadors for Texas Children's Hospital has been the voice of patients of Texas Children's, one of the nation’s finest specialty hospitals.

Ensuring that the kid patients receive the best possible care, Ambassadors pledge to stand and speak up for them both through their own charitable donations and by being socially engaged with the greater Houston community, enlisting others to aid in the cause.

Ambassadors, who also work with the hospital to define its most critical priorities, have given millions of dollars to provide support where it's needed most.

Two annual Ambassadors On Call luncheons spotlight the hospital by featuring special guest lecturers and renowned health experts, question-and-answer sessions with leading scientists and physicians, and behind-the-scenes tours of operating rooms and research facilities.

The annual, family-oriented "party with a purpose" celebrates the work done by the Ambassadors on behalf of Texas Children's. To teach the next generation about philanthropy, the price of admission is one donated book, and the day is filled with unique activities and opportunities to meet new friends and spend time with old ones.

Vote now for Ambassadors for Texas Children's Hospital — or one of the other worthy local nonprofits — in the CultureMap Charity Challenge.