http://aescripts.com/un-precompose/

Un-precompose is simply the reverse of the built-in After Effects functionality "Pre-compose".  Pre-compose allows you to move all of your selected layers into a new composition, leaving only the composition layer in the original timeline.  Un-precompose allows you to pull all of those layers out of the pre-comp and into your root composition and does its best to do so without affecting the appearance of your content. This includes copying over effects to each of the extracted layers as well as maintaining keyframes and expressions that were previously applied.