- Blekko - a smaller independent search engine.
- DuckDuckGo - a smaller independent search engine.
- Google - the search engine with the largest global reach.
- Internet Archive - if you find broken links you can see what those pages looked like in the past.
- Bing - the default search in Windows. It has around 10 to 15% market share in the US and also powers Yahoo! Search.
How do Search Engines Work?
What are People Searching for?
- Google Keyword Planner - gives 12 months of historical data, requires an AdWords advertiser account which takes $5 to activate.
- Google Trends - a free, but less granular version of Google's keyword data
- Bings Ads Intelligence - a Microsoft Excel plugin offering access to Microsoft's search data, requires a Bing Ads account which takes $5 to activate.
- Various search marketing companies like Wordtracker, WordStream, SEObook, and Wordze also offer commercial keyword research tools.
- DMOZ - Open Directory Project edited by volunteers.
- Yahoo! Directory - one of the oldest web directories
- Wikipedia - similar to DMOZ in structure, but hosts articles instead of just categorized link lists
More Search Engines at:
Validation Service from W3C