Use for: data on advertising spend and agency ranking
The Ad Age Datacenter provides access to current information about advertising spend for top brands and Advertising Age's Agency Report, an annual ranking and analysis of advertising and marketing-services agencies.
Use for: advertising and expenditure monitoring
Kantar's advertising and expenditure monitoring offering tracks a large range of media across more than 20 traditional and digital channels with comprehensive product categories and rate information.
Use for: rates, contacts, and metrics for media buyers
SRDS (an industry standard) provides brands and planning/ buying agencies access to media-specific databases that cover rates and contacts, audience metrics and more, along with education, resources and training tools.
Use for: marketing's point of view of procurement
The Association of National Advertisors communicates marketing best practices. The ANA Procurement Task Force's mission is to "close the gaps on the value of procurement bewteen procurement and intenal marketing."
Use for: trends, benchmarks, adspend, and forecasts
WARC partners with multiple content curators to provide intelligence on trends, benchmarks, adspend, forecasts, and company profiles. The WARC Data offering provides global expenditure data, along with media costs comparisons.
Use for ad agency discovery, trends, costs, contracts
4A's (American Assocaiation of Advertising Agencies) produces surveys on topics relevant to ad agency business, including the state of the industry, agency costs, employee salaries and benefits, and trends.
Use for: staying up-to-date on all thing marketing tech
This excellent blog, edited by Scott Brinker, analyzes topics "at the intersection of marketing, technology, and management." Detailed posts focus on all thing marketing tech, including the popular Marketing Technology Landscape map.
Use for: finding ad agencies (supplier discovery)