ridged fork, suppestion goes agaist the pedaling montion slowing you down not to mention weight
clipless pedals and shoes, alows you to use upstroke while pedaling
wheels, deep dish wheels, bladed spokes, light weight ect. soul 4.0 are the best vaule for money
tires, 23c slick is fastest
fit, get pro fit
aero clip on bars, can speed you up by 2-3mph
good gearing ratio
beyond that weight and aerodynamics. really the biggiest factor is your legs, second would be wheels/tires.