Here is a great starting point thread, it covers almost everything with tons of pics.
The Official Intake Thread
There are three basic kinds; Cold Air Intakes CAI, Short Ram Intakes SRI & Chamber Intakes (and one hybrid Chamber CAI by J's Racing which costs a small fortune). Each system has it's own advantages. Tons of info under the "fit-jdm-tuning-engine-modifications-swaps" thread a few down from this one.