It is probably CV joints.  You could just look under there at the boots to
see if they look broken.  Most of the time they break and then the grease
leaks out and dirt gets in wearing the joints out.  If they are not broken
you can try turning the shaft back and forth to see if there is a noticable
noise or slop.  If you are really broke at the moment you could try using a
grease needle (get from NAPA) and some moly grease in a grease gun.  Use the
needle to squirt some new grease inside the boot and then massage the boot to
get the grease into the joint.  If this quiets things down then you know that
your joints are on the way out and you can start saving up.  I sell rebuilt
axles for $85 with a $55 core charge.  These are rebuilt CV joints (they put
new balls in and rework the grooves) and new boots already installed on a
cleaned up axle.  Or you can get new CV joints with boots for $55 each (two
per axle).  Hope this helps.

Thanks,
Ken Wilford
John 3:16
www.vanagain.com
Phone: (856)-765-1583
Fax: (856)-327-2242