If you wire it into the glove box light it comes on when you turn your lights on. The most natural effect, IMO. Studying the shop manual I found no other easily accessable source switched like this. The factory light kits taps into here as well.

 

i recalculated... 20 for all the interior led's 6 for the switch 10 for the wire and 10 for the battery kit. so it was 46. i thought it was more because we also did his trunk

 

I justdid this using LEDs from Fry's electronics. They sell jumbo white 10mm LEDs that give off a perfect amount of light if you're going for a dim ambient look.

I tapped into the glove box light and used computer fan connectors to make the installation more modular and professional. I aimed the lights at about a 30deg angle down using hot glue as a mount and zip ties to secure the LED. To use the zip ties I drilled two small holes into the lower panel so I could secure the hot glue and LED mounting.

I also used adhesive felt to cover all wires and mountings to prevent any possible squeaks or noises down the line.

Total everything cost about $25 (wires, LEDs, felt, quick release connectors, hot glue) and I am very happy with the turnout.