remove all un-nessesary accessories. a/c, PS, etc... Not only will you remove the weight (a/c weighs just under 40lbs, I don't know how much the PS pump weighs), you'll also reduce parasitic drag on the motor, freeing up maybe 1 or 2 ponies :exnbp:
You can also make a DIY "cold air intake" with some $6 dryer ducting. Coupled with a K&N drop in filter, will probably make another 1 or 2 ponies. To do this mod, you remove the intake resonator chamber from under the airbox (behind the bumper), attatch the ducting to the bottom of the stock airbox with a hose clamp, run the other end through the hole in the sheet metal under the airbox (where the stock resonator came through) and back behind the bumper. It will make the car sound cool, draw in colder air, and with a K&N filter, should make a couple hp. There's a good writeup/pictorial on g2ic.com.