When ever I drive my 97 Chevy Cavalier I always smell gas when I park in the garage.?

could be lots of things ... from very serious to totally harmless (sorry to be vague on about that). I will though out my thoughts in order of my estimation of likelihood ...

(1) gas cap ... most (newer) cars have a pressurized fuel system which means that pressure builds up in the gas tank ... if the gas cap does not seal well you will get gas fumes leaking out especially in hot weather which will be noticeable when the car is parked in an enclosed space.

cheapest way to fix/diagnose this is just to buy a new gas cap (make sure it is the correct one ... or it will leak!!)

(2) engine running rich ... unburned gas comes out of the tailpipe. the onboard computer should adjust for this but either something is not working right (oxygen sensor, dirty fuel injectors?). this may be the case only when the car is cold ... just when you start the vehicle ... i.e. while it is standing in the garage. emissions check would rule out this.

(3) gas tank, fuel line or fuel pump leak ... least likely but most hazardous from point of view of fire or explosion.

finally, it is very unlikely that gas "running" out of your car anywhere (even if people like to jokingly say there car is leaking gas) so it is unlikely that you will see it.

definitely take it to a mechanic if you cannot rule out (1) or (2) ... better safe than sorry

good luck!!

added: lol ... yeah, and like the first response says: check for sources of gas smell other than your car! and even if you fix the problem, the smell is likely to linger for quite a while ...

Is your car still on? Do you have a lawnmower in there? How about a tank of gas for your lawn mower?