List of User-Agents (Spiders, Robots, Browser)
Search Engine Land - News On Search Engines, Search Engine Optimization (SEO) & Search Engine Marketing (SEM)
Search engine optimization - SEO Company Search Engine Genie
User Agent Man — A Blog about Client Side Web Technology
UserAgentString.com - unknown version
100 Search Engines - The world's most private search engine
Search Engine Guide: SEO News & Advice for Small Businesses
rapid-search-engine.com - Registered at Namecheap.com
Search Engines Search Engines Search Engines
Search Engine Journal - SEO, Search Marketing News and Tutorials