Article Sciences - Scientific article search and order engine, a service provided by Institut de l'Information Scientifique et Technique (INIST) of Centre National de la Recherche Scientifique (CNRS), France.
CiteSeer - Scientific literature digital library and search engine.
ISI Highly Cited - A search tool to identify individuals, departments and laboratories that have made fundamental contributions to the advancement of science and technology in recent decades.
iSpecies - A species search engine from Rod Page of Glasgow University. Search on either the common or Latin name of a species. Results are generated by querying other data sources.
Science-advisor.net - Scientific search engine and online forum. Researchers and students can search the scientific literature and can freely and anonymously discuss and review research articles.
Scirus - Search engine that fetches only scientific websites.
SciSeek - Science search engine and directory. Also provides forums, tools and related news.