Quiver is an After Effects extension that allows you to apply saved expressions to your layers. It's a huge time saver for me and anyone who uses expressions in their work (hopefully everyone). We've all had the expressions.txt file that we copied and pasted from. I hope you dump it like I did.
Expanding upon the previous version, Quiver 2 allows you to create and modify the txt files containing your library of expressions right from within the panel itself!
This download comes with the extension, a user guide, and a folder of expressions to use in your projects.