This question has been asked several times recently so I thought I would post all the things you could do so I can just cut/paste when it is asked again.

First you need to realize that making some of thse changes will change what clas you run in at your local autocross. And if it is a street car, these will effect the safety of the car. Steel saves lives- fiberglass saves weight.

1. Change the hoods, bumpers, and valances to fiberglass.
2. Switch to a lightweight fiberglass targa top.
3. Change the glass to polycarbonate
4. Remove the carpet, backpad, pass. seat, sun visors, console,
5. Remove the sound pad from the engine compartment
6. When you change the hood to f/g remove the springs and hardware.
7. Remove the fresh air fan from under the front hood.
8. Replace the heater boxes with a header.
9. Remove the windshield washer system
10. Remove the headlight motors and assocated stuff
11. Remove the arm rests from the door panels
12. Change to early doors w/o the steel beam
13. Remove the door windows and cranks.
14. Remove the heat shield which is over the muffler
15. Remove the sound deading material and any undercoating
16. Remove the seam sealer that cover the welds in the trunks
17. Some think f/g rocker panels save weight over the stock ones. It is true they are lighter but not by much.
18. Aluminum wheels.
19. Racing slicks are at least half the weight of a street tire.
20. Install a racing battery. Saves 15-20 pounds easy.
21. About half the wiring can be cut out.
22. Remove the cover plates from the back side of the brake rotors.
23. Grind/cut off all the brackets/bolts/tabs/ etc that are everywhere on the car.
24. Remove glove box and door.
25. Install f/g door skins