Toolmonger has a blog post about 2 different types of router bit guides that you can check out:
I think these could be useful in the shop. However, I also wonder if it would be possible, or rather worth the work to create one in house that used common router bits, with common depths. It might not be as slick as a store bought one, but could be handy. It could be made on a per project basis - I have often routed an extra piece when I knew I would need to match it in the future to test the depth on.