Hunch says its algorithm is a mathematical framework married with a group of users who provide "personality by contributing to it and making it clever, funny, and nuanced."

Scirus is a playground for all things scientific. The site searches more than 485 million science-specific Web pages and is built on technology developed by Fast Search and Transfer, now owned by Microsoft. The Scirus engine focuses only on Web pages containing scientific content. If users search for REM they won't see any results for the popular band.

The search engine picks up peer-reveiwed articles such as PDF and PostScript files and dives into digital archives and patent and journal databases.

Scirus has a range of subject areas including health, life, physical and social sciences. Users can rank results by relevance or by date.