Biocrawler
http://www.biologie.de/
German Directory and search engine for biological information.
Chemie.DE
http://www.chemie.de/
Directory and search engine for information about chemistry.
Scirus
http://www.scirus.com/
Scirus combines a targeted crawler from FAST that focuses only on web sites with scientific content.
Search4Science
http://www.search4science.com/
Search4Science is a search engine put together by scientists for scientists.
Biolinks
http://www.biolinks.com/
A search engine for scientists. It spiders the web and has human-categorized results.
SciSeek
http://www.sciseek.com/
SciSeek is a focused scientific area.
iCivil Engineer
http://www.icivilengineer.com/
Internet resources of civil engineering technology; covering all disciplines: architectural, construction,
environmental, geotechnical hydraulic, structural, surveying and transportation
MathRix
http://mathrix.virtualave.net/
MathRix is a directory of web sites in French and about mathematics.
PSI - Polymer Search on the Internet
http://www.polymer-search.com/
Search engine for the global polymer, plastic and rubber industries. Includes daily industry news.
SStreams
http://www.sstreams.com/
A directory of technical computing oriented links. Top categories are
high-level programming languages like MATLAB, LabVIEW, Mathematica, and others. | 
