I haven't found a glitch thread for Xbox, so here...
If there is one, I'm sorry. Delete this one.
Here's a glitch I found:
I did it while in the monster truck. I noticed that if I hit some cars just right, they would launch straight into the air. My guesstimate would be about 100-150 feet.
The second one, also caused by running over cars in a monster truck, was that the car would sink into the ground.
like so:
car 1:

car 2:

car 3: (this is the only one that blew up)
*image removed by me due to newbie disadvantages
same car, without fire:
*image removed by me due to newbie disadvantages
As you may have noticed, this only worked with Tahomas.