THE search engine. This is for discussion about Google as a company, not for discussion of individual sites (SEO, PageRank for a site or "why a site ranks where it does" questions) or Google search results.

Sub-Forums: AdSense, AdWords, Analytics, Sitemaps, Google APIs, Product Search

For anything related to Yahoo as a company or their search engine. This is not for anything regarding the Yahoo Directory or questions about why you rank somewhere specific in the Yahoo search engine.

Sub-Forums: Publisher Network, Search Marketing, Yahoo APIs

For discussion of Microsoft (as a company) and their search engine that powers the Bing search.

Sub-Forums: adCenter

Any search engine without their own forum, can be discussed here.

Directories (such as DMOZ/ODP, Google Directory, Yahoo Directory, etc.) can be discussed here. This is only for sites that are only directories, not sites that have a directory somewhere within them.

Sub-Forums: Solicitations & Announcements, ODP / DMOZ