I changed all my interior bulbs for white LEDs when I first got my car. I actually did a How To on the rforum - but I've accidentally deleted all my photobucket pictures, so it's pretty pointless now.
2 x 501 in overhead light
3 x 501 in rear overhead light.
1 x 501 in each footwell
1 x 501 in glove box
1 x festoon in each vanity mirror
There's also 1 x 501 in each wing mirror that I've never got round to changing as I was scared I broke the glass when taking it off!