What could the clunking sound be in my front end?

That sound in the front of your car could be caused by worn ball joints, but it also could be caused by badly worn struts (shocks), or other front end parts. You need to have it checked out by someone who knows what to look for. In a worst case situation, the front tires could fall off. Even if it is not serious, you don't need to change parts unless you know that they are bad ( parts are expensive and labor is more expensive ). Most tire places may inspect it for nothing just to get your business, but beware that some places may change things that are not bad just to pad the bill. Talk to people you know and see if you can find an honest dealer. Most cars have upper and lower ball joints. Not all of them go bad at once usually. A good mechanic can check and see if any are bad. Good luck.