I just finished converting the lights on my car to LEDs, (Interior, trunk, parking lights and license plate), and it cost me exactly $30.48 shipped. I think this is a lot cheaper than all the "LED Conversion" kits being offered on here and a lot cheaper than any of the LED stuff I found on most automotive websites.
Since I'm a nice guy, I'm going to share exactly what I ordered and where. I will also give a brief review. I hope someone out there will find this useful and save some money at the same time. If that's you, please send some rep my way.
A couple things to note:
Sorry in advance for the horrible horrible photos. I have no idea what settings to make my camera to get these shots. Anyways... they're good enough for you to get an idea how they look.
1) Prices may change from the time of this post. It shouldn't vary too much though.
2) Shipping is straight from China so it will take about 2-3 weeks for most orders to arrive, unless you pay a little extra to expedite in which case it'll take 1-2 weeks.
3) Dealextreme has a ton of automotive LEDs so you don't have to get exactly what I got, you may even find cheaper ones on there than what I got. Use what I bought as a reference to know exactly how it fits.
Interior/ Dome Light:
2.5W 20x5050 SMD LED 270LM 8000K White Car Reading/Dome/Combination Rear Lamp Light (DC 12V)
Price: $8.99 ea
Qty: 2
Review: The light is super super bright. It's blinding. Seriously. Anyways, it's a little big. In order to make it fit, I had to cut off that little tab inside that switches on the light when you press it. If you don't want to cut anything, I suggest you get the light that I used for the trunk. See below. That one should fit without any problems.
Trunk Light:
T10/BA9S/Festoon 1.8W 12V 12-LED 60000mcd Car Ceiling Dome Light Bulb - White Light
Price: $6.10 ea
Qty: 1
Review: A lot brighter than stock. I had to sand down the circuit board a little bit in order to fit it into the stock housing. This is probably the max light you can get from the trunk light.
License Plate Light/ Parking Light:
T10 1.2W 6500K 70-Lumen 5-SMD LED Car White Light Bulbs (Pair/DC 12V)
Price: $3.20/ pair
Qty: 2 pairs
Review: Again, a lot brighter than stock. I like the fact that it nicely lights up the license plate and not the ground. For one that seems like a distraction for cars behind me and also I think it's kind of ricey. Overall, it's very white and clean even lighting.
Enjoy!