Check your sway bar links. its a 22 dollar fix from autozone.
the sway bar links on these cars are known to bust.
To check the links, http://i96.photobucket.com/albums/l185/brandnew161/0407081859a-1.jpg.
should look about like what's circled in red.
you'll need to first jack you car up to unload the suspension.
take your wheel off and yank on the thing to no end, also examine the bushings, if they are shot(like mine were), it's probably a good idea to replace them. While jerking that thing around if you can re-create the noise you're hearing you'll know that you need to change them.
In the case of mine i couldn't tell until i put a wrench on one and tried torquing it, then it made the loud, signature *CLUNK* as if i was driving over a bump.
easy fix, 2 bolts on each side. bolts may be seized on. buy some PB blaster and blast the sh*t out of them.
make sure to re-torque them after 20 minutes of driving.
your focus should drive smooth as butter and be quiet as @&$$ :)