Can you point me in the right direction where I can find top landing page designs for the typical campaigns: contact us, become a partner, free trial, and then for the usual asset types: whitepapers, analyst reports, eBooks, webinars?
I'm not sure about a collection of top designs. But I found the below to be helpful
You can sign up for a free trial of Knak and they have different landing page templates for different purposes, you don't have to pay to see all the designs.
Sort of similar, you can sign up for a free account with Unbounce and they have tons of landing page designs by use case.
Hope that helps.