Mislav Kos of Soliant Consulting wrote a very handy, modular script that tells you which layouts contain a particular field:
I wrote a blog post last month showing a way to quickly find where unstored calcs and summary fields are being used in a solution. This post is a sort of follow up, in that here we once again look at a way of quickly finding something out about a solution that would otherwise require a DDR.
Have you ever worked on a solution and had to make a change that involved a field in some way, and the change required that you find all the other places where that field was being used? For example, suppose that a full name field is being split into first and last name fields. You need to find what layouts the old field is on, so that you can add the new field accordingly.
Follow the link for more information and to download the file with the script.