^^^lol
This is my kind of thread!
As tisguy said, it depends on how far you want to go with it.
As TegSox said, you can probably save 50-100lbs just in removing the stuff he mentioned.
If you want to go all out (like me and a few others), there's A/C, P/S, heater core, blower motor, dash vents, interior paneling (I kept the front half but everything else is gone), and even go as far as cutting certian parts of the interior subframe out (as long as you have proper re-enforcements in other ways like a cage or something), get rid of misc. brackets and clips, and replacing OE panels with lighter carbon fiber or possibly fiberglass, lighter wheels, get rid of the glass and put in some FAL windows, the list goes on and on...depends on how far you want to go.