Q:
What are the best sourcebooks and websites for a photographer to spend their marketing dollars?
A:
Shooting tests is where you should spend your marketing budget, as that is the most direct path to getting jobs. Once your portfolio is where you want it to be, I would suggest the following US options in the commercial advertising world:
At-Edge, Found, Blvd, Wonderful Machine, Production Paradise, Workbook, Drip, LeBook, (new) Komyoon, Altpick, Lurzer Archive, PhotoServe, and Creative Hotlist.