Source: Hitching a ride. - Funny Pictures
Stashed in: Lolcats!, gifs, Goats!
YouTube videos of cats riding things.
A Tumblr search of "cats riding things" reveals... only a video version of your gif.
Luckily, Memetastic has Paula Deen riding a cat:
How can you talk if you haven't got a brain? ~Dorothy to the Scarecrow in The Wizard of Oz
Lost in Translation Bill Murray upvote gif
Golazo Soccer Goal gif
Gravity Tear Drop In Space gif