IMHO
A common source of burinng is when road debris (like plastic bags) are swept up under the car and contact the catalytic converter. The cat is very hot (~900 degrees internally). Get under the car and look at your exhaust -- with it not running, unless you're crazy like me, and look for items stuck to the cat or on any other part that gets hot.
If the car is running and you can't see the source of the smoke looking in the engine compartment make sure you're not leaking oil. Look for changes in the amount of oil under the car when parked in a clean spot. A common problem is that oil or grease gets on a rotating part and is slung around -- contacting a hot exhaust part. That will cook off making smoke. if someone just changed the oil, they may have spilled some causing this.
Check you wheels. Make sure you're not leaking brake fluid (which should be announced beforehand by poorer braking action) -- or that there is no fluid visible near your rotor or brake calipers.
Look more carefully for wires or hoses that may be loose.
CAREFULLY observe your drive belt. Look for evidence of glazing or wear. Check to make sure the tension is right. Important: RUN THE ENGINE and make sure the belt and all of the pulleys that it contacts are is turining. You could have a frozen alternator pulley and your belt could be just rubbing away at it (instead of turning it). That could make smoke.
Hope this helps.
