Depends on how low you want to go, your daily driving habits and what you want to do.
I've gone from OEM, to Eibach's, to Tein S-Techs. If you don't want to get coil-overs ( a worthy investment), you could opt for lowering springs, which are cheap.
Here is a chart for you, to see what each spring will lower your car by
TEIN S-tech: (front)2.32" (rear)2.4"
TEIN H-tech: (f)1.73" (r)1.81"
TEIN SS adjustables: (f)1.14" - 3.03" (r)1.54" - 3.8"
Sprint: (f&r)1.75"
Progress: (front)1.8" (rear)1.7" (settles at about 2.2")
Hotchkis: (front)1.75" (rear)1.5"
TRD: (front)1.25" (rear)1.25"
Eibach Pro 
front)1.1" (rear)1.1"
Eibach Sportlines: (front)2.1" (rear)1.75"
H&R sports: (front)1.25" (rear)1.25"
H&R race: (front)2.0" (rear)2.0"
---------------------------- here is my experience
I live in Canada, where there is snow and crap..and at first i was too chicken to lower it. then i though man..the car look soo dumb, cause its sits so high..a car with nice rims and a 4" gap is not hott at all. so i played it cautious and got the eibachs which only lower the car an inch or so...i liked it andd all but it wasn't satisfying enough. I would always look at it, and go..humm is it lowered..i dunno..i guess u couldn't really tell it was lowered until u parked next to a corolla...so then i was like screw this and went down to s-techs which dropped the car to about 2.4" and all i can say is ..crap..it looks smokin.. all i have to say is as far as cheap drop goes...go for tein s-techs i think you will be satisfied once you do.
that's what s-techs look like on my car