I'd like to find a list of ALL websites that use CCBill. On the CCBill
website they have a search function for finding both general and
mature content sites but you can't just see a list or a directory of
sorts to see what the sites are, you have to use a keyword to search
for them.

Google will have a few of them. Use the search term ' inurl:/ccbill/ '
Link: ://www.google.co.uk/search?q=inurl:/ccbill/&hl=en&lr=&start=10&sa=N
This link takes you to the second page of results, as the first is all
CCBill.com