System to track what Zip Codes my vendors service I am designing a table configuration that will contain all of the zip codes in the United States. I have a .csv file of all the zip codes in the U.S., so thats at least a start.

This will end up as a one-to-many relationship between our vendors (they are waste services companies), and the various zip codes they service. Does anyone have advice on a good way to set up the tables to track this data? Some vendors may only service 5-10 zip codes, while the national players can handle nearly all 45,000 zip codes, so I'd like to set it up in a manner that this does not become a nightmare later on. 

Any advice is appreciated!
I would say you would have:

Table: vendor
  id, name, etc

Table: vendor_area 
  id, vendor_id, area_code_id

Table: area_code
  id, area_code, country_id, region_id (etc)

I'm suggesting that not knowing your business. But I would hate you go in a naive route assuming that you'll do US only and in a couple year you have to redesign the whole thing. The above will give you flexibility to expand and add more meta data to your areas/regions being covered.