Maxey Park is the first City of Houston Park to feature an official dog park area for canine visitors. Between 12 and 13 acres of parkland have been designated as a dog area.  This area features a fenced-in space for the dogs to exercise off leash, and amenities include doggie drinking fountains, separate large and small dog areas, doggie shower, information kiosk, shaded areas, doggie waste disposal station and benches throughout the space.
Maxey Park, 601 Maxey Road (Key Map 496C)

Ervan Chew Park (4502 Dunlavy) is the first 'neighborhood' park in Houston to allow dogs to legally run free, off-leash.  The dog zone, which is located adjacent to the picnic area and swimming pool, is a fenced-in space, approximately 9,000 square feet in size and is designed to allow dogs to exercise freely.   The Ervan Chew Park dog zone was the first step in providing an area for off-leash dogs.
NO Children under 12 allowed.
4502 Dunlavy (Key Map 492Z)
The Friends of Ervan Chew Park, a neighborhood organization, provided funding for the dog zone.  

Katy Dog Park
City of Katy, Texas. It is located at:
5414 Franz Road, Katy, Tx. 77493
(Between the Harris Co. Katy library and the Katy police station.)
There is one sign in front of the park between.
At this writing(1-07) there were no other signs with hours, rules, etc.
About 14 acres with shade trees.
A pond, benches and agility equipmet are to be added.
Thanks to Robert for this posting!

Levy Park Dog Park
3801 Eastside, 1 block South of Richmond (between Kirby & Buffalo Speedway.)
Some shade, dog water fountain, a lot of parking.
Small area set aside for dogs and with owners.

City of Bellaire
"Officer Lucy Dog Park"
The Bellaire dog park was named in honor of Officer Lucy,
Bellaire's K-9 detective who passed away recently of natural causes.
Located in Lafayette Park,   4337 Lafayette
**Large dog and small dog areas
**Some shade in large dog area,  water available.
Double gated & fenced, pick up bags,
This is a small neighborhood park.
For more information on the dog park,  call
Bellaire Parks & Recreation Dept.at 713-662-8280.
NO Children under 12 allowed.
Rules

The Woodlands has 2 small parks
Cattail Park
NO Children under 9 allowed.
North side of Research Forest Drive, west of Shadowbend and I-45.
In the Bear Branch Park Complex near the swimming pool.
AND
Bear Branch Park
NO Children under 9 allowed.
It is over 2 shady acres, and it is separated into a large dog section and a small dog section.
( Per Parks Dept Rules: 25lbs and under qualifies as small ).
There is water available in both areas, many benches and dog waste bags and waste containers.
Bear Branch Park is on the NORTH side of Research Forest Drive, west of Shadowbend
MAP
The Woodlands Dog Park Club....Woodlands Dog Park Events

Millie Bark Park (Precinct 3) - 15 FENCED Acres
'Separate' areas for Small AND for Large dogs.
Water fountains for you and your dog
Doggy Shower (Bring your own towels)
On Westheimer.
When entering the Park near Westheimer and Hwy.6
(north of "West Oaks Mall" and West of "Best Buy" and
"Barnes and Noble" in the shopping center at Hwy.6 and Westheimer).
The site for the dog park is located between the two ponds on
the south side of Westheimer Parkway.  Rules
Thank You, Steve Radack Commissioner of Precinct 3 !!!!

Bear Creek area Dog Park(Precinct 3)
About 17 acres include 'Separate' large and small dogs area
Each of the 2 areas has a pond shaped as dog biscuit.
Doggy rinse area - (Bring your own towels)
Benches are somewhat covered areaes under a canopy.
Open 7 days a week - - 7 am. to dusk, 
Thank You, Steve Radack Commissioner of Precinct 3 !!!!

2nd Precinct 3,  "D. J. BARK Park" -
Westpark Drive Just inside the loop and just South of 59 - under the power lines, on Westpark Drive between Loop 610 and Loop Central.
Double gated entrance, separate large dog & small dog areas each area with a pond, walking path,. newly planted trees, benches, water drinking fountains & poop pick up bag stations.
The parking lot, on a site rented(The parking site was NOT donated) from Center Point Energy, will serve the parks, with spaces for about 100 vehicles. Rules

Pearland has TWO Dog Parks
1st Pearland Dog Park:
Located off 288 in Pearland (you can see it from the east side of the highway) between FM 518 and Shadow Creek, or between the FM 518 and McHard exits.
The dog park takes up the south end of a community park.
Benches and a shade canopy.
Also there is some agility equipment for having fun and to build your dog's confidence.
Restrooms and parking are provided in the general area of the park.

2nd Pearland Dog Park:
Located at Independence Park on Liberty Drive on the city's east side.
3919 Liberty Drive
1.5 acre park has separate areas for large and
small dogs, and also has an obstacle course and benches.

Alvin Dog Park
Prairie Dog Park
This 1.1 acre park is located at 575 East Hathaway and is next
to the Alvin EMS facility. Park has playground, swings, picnic tables, parking and
Hike & Bike Trail.
Alvin

Deer Park, Texas
Ella and Friends Dog Park
2 acre dog park in Deer Park on 13th Street 
West of Center next to the Jimmy Burke Activity Center.
The park features a sandbox, numerous fire hydrants, and lots of shade trees. Park benches and water fountains for both owner and pet.. If a pooch makes a "deposit," there are free, plastic bags for pickup and several waste bins for disposal.
Dogs must be registered with the city and have updated vaccinations.
Registration can be obtained for $5 at the Animal Shelter on Luella.
Constructed by Deer Park Rotary Club and the City of Deer Park
7-28-06 - Thanks to Aaron  for this news!

Jackson Dog Park
Located on Westpark Drive between Loop 610 and Loop Central.
(Inside the loop and South of 59,  under the power lines.)
Separate large and small dog areas, each with a pond, small trees and benches.
Soon may be somewhat noisy since a children playground soon to be added next to it

SugarLand area is working on having a dog park.
It is to be a part of Brazos River Park to be located close to Uof H SugarLand campus.
Please check back.