It is probable bent or the bearings are shot.

You should tighten your spokes

Actually. it's most likely the hub. Take the wheel off the frame and there should be an inner nut on the axel. Tighten down the inner nut just enough to eliminate wobble, but be careful not to tighten too much or you'll get resistence making it difficult for the wheel to turn.

i am doing a school project on making bicycle indicators and any pictures or infromation on this topic would help me alot!! if you would e-mail me back with more pics than infromation or a few websites that may be helpful i would appericate it thanks
SEAN PAUL MILLER
BELFAST
NORTHERN IRELAND

you should check the berings