http://www.intimations.org/fanfic/supernatural/More%20Than%20Meets%20The%20Eye.html

Transformers crossover, wincest by Astolat.

http://delicious.com/lapillus/impala all of the Impala as a major character, usually a sentient one, and occasionally one transformed into a human.

http://secondplatypus.livejournal.com/19258.html
This has Dean/Castiel in it, but the car prevents anything from happening. It is told from her perspective.

http://delicious.com/sams1ra/metallicar
9 fics centering around the Impala

I love this (http://merryish.livejournal.com/303701.html).

Self-pimp here: I have a series of drabbles, like a Impala-journal, that goes from the first owner to the series final (it was written last year, so, it's a bit AU now). http://adrenalineshots.livejournal.com/39234.html#cutid1