Short "ow" sound:
* How
* Now
* Cow
* Vow
* Bow (as in a bow tie)
* Crowd
* Powder
* Flower
* Shower
* Tower
Words with "ow" representing a different sound:
* Grow (long "o" sound)
* Know (long "o" sound)
* Blow (long "o" sound)
* Slow (long "o" sound)
* Snow (long "o" sound)
Keep in mind that the spelling "ow" can represent different vowel sounds depending on the word.