I recently picked up some LED interior bulbs for my Civic. These things are a nice upgrade. Depending on what type of bulbs your car uses you can get significantly whiter, brighter light with LEDs. This car has two map lights and a dome light, I took some pics of the map lights with the stock incandescent bulb on the driver's side and the LED on the passenger side. These bulbs consist of four LEDs on a small circuit board. Color is cool white.
I also upgraded the trunk bulb. Stock bulb is a little 194. The site I ordered from has oversized replacements with a standard base, so I picked the biggest one that would fit in the bulb housing.
The results are pretty impressive:
BEFORE
AFTER
Both those pics were taken with the camera at the same exposure.
LEDs also use less power of course, and should last a lot longer. The map and dome bulbs for my car were $7 each, and the bulb in the trunk was $12.