Whats the next big thing in automotive lighting? LED's. Cooler running, lower power consumption, fast "flash off", longer usable life, in recent years manufacturers have slowly been replacing their standard incandescent & halogen bulbs with LED arrays to take advantage of the benefits. The aftermarkets not far behind, offering replacement bulbs to fit almost all makes and models into standard housings.
Compatibility with factory housings is especially good news for headlamp upgrades! Normally you'd install a HID which is too long for the housing, placing the bulb outside the "sweet spot" for the reflectors causing glare for oncoming traffic and poor projection. An alternative is to use projector replacement housings, but they're expensive, require considerably more work and typically are poorly constructed with cheap materials.
Finally you might consider a high output halogen, these run hotter than standard bulbs and risk yellowing or melting the housings.
So here's a demonstration of LED's installed into OEM housings on a Chevy Aveo.