Rear end of my car is somewhat "loose", creaks when I take off
 

Any pointers? doesn't make any noise over bumps and overall feels fine city driving, but I feel it WOT and around fast corners, my buddy noticed WOT in 3rd going over barely uneven pavement the rear end kicked out some, diff bushings?

Jack up the car, and put it on jack stands with the suspension unloaded. Then and get under there and start wiggling suspension parts. It shouldn't take long to find whatever is loose.

If you are too lazy to do it yourself, take it to an alignment shop.

Check your tire pressures first.

<edit>

Sorry, I didn't notice "creaks" in the title before. Yeah, check everything in the suspension.